Photo: Ivan Sekretarev, ASSOCIATED PRESS  Russian opposition leaders Boris Nemtsov, center, and Garry Kasparov, second left, attend a massive protest against Prime Minister Vladimir Putin's rule in Moscow, Saturday, Feb. 4, 2012. Tens of thousands of Russians flooded downtown Moscow on Saturday to demand an end to Putin's rule, casting a strong challenge to his bid to reclaim the presidency in March. Saturday's crowd appeared to be even bigger than two similar rallies held in December, despite temperatures plunging to minus 20 C (minus 4 F). (AP Photo/Ivan Sekretarev)  Russian opposition leaders Boris Nemtsov, center, and Garry...  Russian opposition leaders, Boris Nemtsov, right, and Vladimir Ryzhkov, left, stand in front of a poster reading "This election is farce! " during a rally in Moscow, Russia, Monday, Dec. 5, 2011. Several thousand people have protested in Moscow against Prime Minister Vladimir Putin and his party, which won the largest share of a parliamentary election that observers said was rigged. It was perhaps the largest opposition rally in years and ended with police detaining some of the activists. A group of several hundred then marched toward the Central Elections Commission near the Kremlin, but were stopped by riot police and taken away in buses. Estimates of the number of protesters Monday night ranged from 5,000 to 10,000. They chanted "Russia without Putin." (AP Photo/Ivan Sekretarev)  Russian opposition leaders, Boris Nemtsov, right, and Vladimir...  Russian riot policemen detain an opposition supporter during a demonstration, outside Moscow's iconic television tower in Moscow on March 18, 2012. Riot police arrested dozens of protesters today who picketed Moscow's iconic television tower after footage purporting to show people being paid to rally against Vladimir Putin was aired nationally. An AFP correspondent saw organisers Boris Nemtsov and Sergei Udaltsov being led away with about 30 others sporting the white protest ribbons of the nascent movement against Putin's 12-year domination of Russia. AFP PHOTO / ALEXEY SAZONOV (Photo credit should read Alexey SAZONOV/AFP/Getty Images)  Russian riot policemen detain an opposition supporter during a...  An officer of OMON, riot police, (2nd R) chases an anti-Putin protester (R) at the Tverskoi Boulevard in central Moscow, on May 7, 2012. Moscow police said today they had arrested 120 people, including opposition leader Boris Nemtsov, during an unsanctioned rally against newly-elected President Vladimir Putin's Kremlin inauguration. AFP PHOTO / ANDREY SMIRNOV (Photo credit should read ANDREY SMIRNOV/AFP/GettyImages)  An officer of OMON, riot police, (2nd R) chases an anti-Putin...  Police and medics surround the body of Boris Nemtsov, a leading opposition figure and former deputy prime minister, who was shot and killed near the Kremlin, Moscow in the early hours of Saturday, Feb. 28, 2015. Nemtsov, a sharp critic of President Vladimir Putin, was killed early Saturday. His death comes just a day before a major opposition rally in Moscow.  Police and medics surround the body of Boris Nemtsov, a leading...  COORECTING BYLINE Russian riot policemen detain an opposition Left Front movement leader, Sergei Udaltsov, during the demonstration outside Ostankino tower which aims to cap a growing campaign for Russians to boycott NTV television, in Moscow on March 18, 2012. Riot police arrested dozens of protesters today who picketed Moscow's iconic television tower after footage purporting to show people being paid to rally against Vladimir Putin was aired nationally. An AFP correspondent saw organisers Boris Nemtsov and Sergei Udaltsov being led away with about 30 others sporting the white protest ribbons of the nascent movement against Putin's 12-year domination of Russia. AFP PHOTO / ANDREY SMIRNOV (Photo credit should read ANDREY SMIRNOV/AFP/Getty Images)  COORECTING BYLINE Russian riot policemen detain an opposition Left...  Police and medics surround the body of Boris Nemtsov, a leading opposition figure and former deputy prime minister, who was shot and killed near the Kremlin, Moscow in the early hours of Saturday, Feb. 28, 2015. Nemtsov, a sharp critic of President Vladimir Putin, was killed early Saturday. His death comes just a day before a major opposition rally in Moscow. (AP PHOTO/Alexander Roslyakov)  Police and medics surround the body of Boris Nemtsov, a leading...  An opposition supporter carries a poster during a rally in front of the television broadcasting center in Moscow on March 18, 2012. Riot police arrested dozens of protesters today who picketed Moscow's iconic television tower after footage purporting to show people being paid to rally against Vladimir Putin was aired nationally. An AFP correspondent saw organisers Boris Nemtsov and Sergei Udaltsov being led away with about 30 others sporting the white protest ribbons of the nascent movement against Putin's 12-year domination of Russia. AFP PHOTO / ALEXEY SAZONOV (Photo credit should read Alexey SAZONOV/AFP/Getty Images)  An opposition supporter carries a poster during a rally in front of...  Flowers lie on the ground as Russian police officers stand near the place where Boris Nemtsov, a former Russian deputy prime minister and opposition leader, was kiiled at Red Square with the Kremlin Wall in the background in Moscow, Russia, Saturday, Feb. 28, 2015. Nemtsov, sharp critic of President Vladimir Putin, was gunned down Saturday, just a day before a planned protest against the government. The death of Nemtsov ignited a fury among opposition figures who assailed the Kremlin for creating an atmosphere of intolerance of any dissent and called the killing an assassination. Putin quickly offered his condolences and called the murder a provocation.  Flowers lie on the ground as Russian police officers stand near the...  CORRECTING BYLINE Opposition Left Front movement leader, Sergei Udaltsov, flashes a victory-sign as he is detained by Russian riot policemen in Moscow on March 18, 2012, during a demonstration outside Ostankino tower which aims to cap a growing campaign for Russians to boycott NTV television. Riot police arrested dozens of protesters today who picketed Moscow's iconic television tower after footage purporting to show people being paid to rally against Vladimir Putin was aired nationally. An AFP correspondent saw organisers Boris Nemtsov and Sergei Udaltsov being led away with about 30 others sporting the white protest ribbons of the nascent movement against Putin's 12-year domination of Russia. AFP PHOTO / ANDREY SMIRNOV (Photo credit should read ANDREY SMIRNOV/AFP/Getty Images)  CORRECTING BYLINE Opposition Left Front movement leader, Sergei...  Russian police officers stand next to traces of the body of Boris Nemtsov, a former Russian deputy prime minister and opposition leader, at Red Square with the Kremlin Wall in the background in Moscow, Russia, Saturday, Feb. 28, 2015. Nemtsov, sharp critic of President Vladimir Putin, was gunned down Saturday, just a day before a planned protest against the government. The death of Nemtsov ignited a fury among opposition figures who assailed the Kremlin for creating an atmosphere of intolerance of any dissent and called the killing an assassination. Putin quickly offered his condolences and called the murder a provocation.  Russian police officers stand next to traces of the body of Boris...  Russian riot policemen detain an opposition Left Front movement leader, Sergei Udaltsov, during the demonstration outside Ostankino tower which aims to cap a growing campaign for Russians to boycott NTV television, in Moscow on March 18, 2012. Riot police arrested dozens of protesters today who picketed Moscow's iconic television tower after footage purporting to show people being paid to rally against Vladimir Putin was aired nationally. An AFP correspondent saw organisers Boris Nemtsov and Sergei Udaltsov being led away with about 30 others sporting the white protest ribbons of the nascent movement against Putin's 12-year domination of Russia. AFP PHOTO / ALEXEY SAZONOV (Photo credit should read Alexey SAZONOV/AFP/Getty Images)  Russian riot policemen detain an opposition Left Front movement...  A municipal worker washes the place where Boris Nemtsov, a former Russian deputy prime minister and opposition leader, was kiiled at Red Square with St. Basil Cathidral in the background in Moscow, Russia, Saturday, Feb. 28, 2015. Nemtsov, sharp critic of President Vladimir Putin, was gunned down Saturday near the Kremlin, just a day before a planned protest against the government. The death of Nemtsov ignited a fury among opposition figures who assailed the Kremlin for creating an atmosphere of intolerance of any dissent and called the killing an assassination. Putin quickly offered his condolences and called the murder a provocation.  A municipal worker washes the place where Boris Nemtsov, a former...  CORRECTING BYLINE Russian riot policemen detain an opposition supporter in Moscow on March 18, 2012, during a demonstration outside Ostankino tower which aims to cap a growing campaign for Russians to boycott NTV television. Riot police arrested dozens of protesters today who picketed Moscow's iconic television tower after footage purporting to show people being paid to rally against Vladimir Putin was aired nationally. An AFP correspondent saw organisers Boris Nemtsov and Sergei Udaltsov being led away with about 30 others sporting the white protest ribbons of the nascent movement against Putin's 12-year domination of Russia. AFP PHOTO / ANDREY SMIRNOV (Photo credit should read ANDREY SMIRNOV/AFP/Getty Images)  CORRECTING BYLINE Russian riot policemen detain an opposition...  Russian opposition leader Ilya Yashin, center, reacts as police investigate the the body of Boris Nemtsov, a former Russian deputy prime minister and opposition leader at Red Square in Moscow, Russia, Saturday, Feb. 28, 2015. Russia's Interior Ministry says Boris Nemtsov, a leading opposition figure and former deputy prime minister, has been shot and killed near the Kremlin. Nemtsov, a sharp critic of President Vladimir Putin, was killed early Saturday. His death comes just a day before a major opposition rally in Moscow.  Russian opposition leader Ilya Yashin, center, reacts as police...  Russian riot policemen detain an opposition supporter in Moscow on March 18, 2012, during a demonstration outside Ostankino tower which aims to cap a growing campaign for Russians to boycott NTV television. Riot police arrested dozens of protesters today who picketed Moscow's iconic television tower after footage purporting to show people being paid to rally against Vladimir Putin was aired nationally. An AFP correspondent saw organisers Boris Nemtsov and Sergei Udaltsov being led away with about 30 others sporting the white protest ribbons of the nascent movement against Putin's 12-year domination of Russia. AFP PHOTO / ALEXEY SAZONOV (Photo credit should read Alexey SAZONOV/AFP/Getty Images)  Russian riot policemen detain an opposition supporter in Moscow on...  FILE - In this file photo taken on Sunday, May 6, 2012, Opposition leader Boris Nemtsov uses a loud speaker during an opposition rally in downtown Moscow, Russia. Russia's Interior Ministry says Boris Nemtsov, a leading opposition figure and former deputy prime minister, has been shot and killed near the Kremlin. Nemtsov, a sharp critic of President Vladimir Putin, was killed early Saturday. His death comes just a day before a major opposition rally in Moscow.  FILE - In this file photo taken on Sunday, May 6, 2012,...  Russian riot policemen detain an opposition supporter during a demonstration, outside Moscow's iconic television tower in Moscow on March 18, 2012. Riot police arrested dozens of protesters today who picketed Moscow's iconic television tower after footage purporting to show people being paid to rally against Vladimir Putin was aired nationally. An AFP correspondent saw organisers Boris Nemtsov and Sergei Udaltsov being led away with about 30 others sporting the white protest ribbons of the nascent movement against Putin's 12-year domination of Russia. AFP PHOTO / ALEXEY SAZONOV (Photo credit should read Alexey SAZONOV/AFP/Getty Images)  Russian riot policemen detain an opposition supporter during a...  Russian riot policemen detain an opposition supporter in Moscow on March 18, 2012, during a demonstration, outside Moscow's iconic television tower, which aims to cap a growing campaign for Russians to boycott NTV television. Riot police arrested dozens of protesters today who picketed Moscow's iconic television tower after footage purporting to show people being paid to rally against Vladimir Putin was aired nationally. An AFP correspondent saw organisers Boris Nemtsov and Sergei Udaltsov being led away with about 30 others sporting the white protest ribbons of the nascent movement against Putin's 12-year domination of Russia. AFP PHOTO / ALEXEY SAZONOV (Photo credit should read Alexey SAZONOV/AFP/Getty Images)  Russian riot policemen detain an opposition supporter in Moscow on...  FILE - In this Nov. 22, 2004 file photo, Boris Nemtsov, a charismatic Russian opposition leader and sharp critic of President Vladimir Putin, right, listens to Petro Poroshenko while Yulia Tymoshenko, left, looks on during a street protest in downtown Kiev Ukraine. Nemtsov was gunned down Saturday, Feb. 28, 2015 near the Kremlin, just a day before a planned protest against the government.  FILE - In this Nov. 22, 2004 file photo, Boris Nemtsov, a...  People lays flowers at the place where Boris Nemtsov, a charismatic Russian opposition leader and sharp critic of President Vladimir Putin, was attacked, at Red Square in Moscow, Russia, Saturday, Feb. 28, 2015. Nemtsov was gunned down Saturday near the Kremlin, just a day before a planned protest against the government.  People lays flowers at the place where Boris Nemtsov, a charismatic...  A Russian family walk to lay flowers at the place where Boris Nemtsov, a charismatic Russian opposition leader and sharp critic of President Vladimir Putin, was gunned down, at Red Square in Moscow, Russia, Saturday, Feb. 28, 2015. Nemtsov was gunned down Saturday near the Kremlin, just a day before a planned protest against the government.  A Russian family walk to lay flowers at the place where Boris...  People react as they lay flowers at the place where Boris Nemtsov, a charismatic Russian opposition leader and sharp critic of President Vladimir Putin, was gunned down, at Red Square in Moscow, Saturday, Feb. 28, 2015. Nemtsov was gunned down Saturday near the Kremlin, just a day before a planned protest march against the government.  People react as they lay flowers at the place where Boris Nemtsov,...  People light candles in memory of Boris Nemtsov, seen behind, at the monument of political prisoners 'Solovetsky Stone' in central St.Petersburg, Russia, Saturday, Feb. 28, 2015. Nemtsov was gunned down Saturday near the Kremlin, just a day before a planned protest against the government.  People light candles in memory of Boris Nemtsov, seen behind, at...  A group of EU ambassadors to Russia lay flowers at the place where Boris Nemtsov, a charismatic Russian opposition leader and sharp critic of President Vladimir Putin, was gunned down, at Red Square, with St. Basil Cathedral in the back and the Kremlin at left, in Moscow, Russia, Saturday, Feb. 28, 2015. Nemtsov was gunned down Saturday near the Kremlin, just a day before a planned protest against the government.  A group of EU ambassadors to Russia lay flowers at the place where...  A Russian police officer stands next to trace of the body of Boris Nemtsov, a former Russian deputy prime minister and opposition leader, at Red Square with the Kremlin Wall in the background in Moscow, Russia, Saturday, Feb. 28, 2015. Nemtsov, sharp critic of President Vladimir Putin, was gunned down Saturday, just a day before a planned protest against the government. The death of Nemtsov ignited a fury among opposition figures who assailed the Kremlin for creating an atmosphere of intolerance of any dissent and called the killing an assassination. Putin quickly offered his condolences and called the murder a provocation.  A Russian police officer stands next to trace of the body of Boris...  A man reacts as he lays flowers at the place where Boris Nemtsov, a charismatic Russian opposition leader and sharp critic of President Vladimir Putin, was gunned down, at Red Square in Moscow, Russia, Saturday, Feb. 28, 2015. Nemtsov was gunned down Saturday near the Kremlin, just a day before a planned protest march against the government.  A man reacts as he lays flowers at the place where Boris Nemtsov, a...  Russian police investigate the the body of Boris Nemtsov, a former Russian deputy prime minister and opposition leader at Red Square with St. Basil Cathidral in the background in Moscow, Russia, Saturday, Feb. 28, 2015. Russia's Interior Ministry says Boris Nemtsov, a leading opposition figure and former deputy prime minister, has been shot and killed near the Kremlin. Nemtsov, a sharp critic of President Vladimir Putin, was killed early Saturday. His death comes just a day before a major opposition rally in Moscow.  Russian police investigate the the body of Boris Nemtsov, a former...
Russian investigators, politicians and political commentators on state television on Saturday covered much ground in looking for the reason Nemtsov was gunned down in the heart of Moscow, but they sidestepped one possibility — that he was murdered for his relentless opposition to Putin.  Nemtsov, a 55-year-old former deputy prime minister and leading Russian liberal political figure for the past two decades, was gunned down shortly before midnight Friday as he walked across a bridge near the Kremlin with a female companion.  The killing came just hours after a radio interview in which he called on Moscow residents to join an opposition rally on Sunday to protest Putin's handling of the economic crisis and his "mad, aggressive and deadly policy of war against Ukraine."  The agency also listed the possibility that the killing was carried out by Islamic extremists angered by Nemtsov's position on the Charlie Hebdo attack in Paris or was connected to the Ukraine conflict, where Russia-backed separatists have been fighting Ukrainian forces since last April.  Nemtsov served as a regional governor and then a deputy prime minister in the 1990s and once was seen as a possible successor to Boris Yeltsin, Russia's first elected president.  "For more than a year now, the television screens have been flowing with pure hate for us," Mikhail Khodorkovsky, the exiled former oil tycoon who spent a decade in prison after challenging Putin, wrote on his website.  On a political talk show on Channel One state television Saturday night, the discussion was framed around the question of "who benefits" from Nemtsov's killing, with the accepted conclusion that it serves only Russia's enemies.  Sergei Markov, a prominent Kremlin-connected political scientist, said he suspected Ukraine's special services of carrying out the attack with the aim of splitting Russian society and bringing a more Western-friendly government to power.