A cyclist passes burned-out buses in Kramatorsk, Ukraine, on Sunday after heavy fighting the previous day. Photograph: Roman Pilipey/EPA  "We have God in our hearts, and they have cockroaches in their brains," said a Cossack military commander who would only give his nickname, "the Diver", and who was speaking into a walkie-talkie outside rebel headquarters in Kramatorsk.  The Ukrainian army entered the city, part of the rebellious Donetsk region, over the weekend but the separatist militias remain in control of their headquarters, a heavily barricaded government building that is surrounded by armed men, as in many other cities across the self-proclaimed People's Republic of Donetsk.  A week before the region is due to have a referendum on seceding from Ukraine, the Ukrainian army is attempting to regain control of key buildings and roads, possibly to stop the referendum from taking place. The separatists say at least 10 people were killed in clashes as the army moved in, although the numbers cannot be verified, and after more than 40 people died in a fire in Odessa on Friday night, the tension in eastern Ukraine is palpable.  "The Diver" confirmed that a key separatist military commander, a man who went by the nickname Romashka ("the Daisy") and was believed to have fought with the Russian military in Chechnya, had been killed by a sniper in Slavyansk on Friday.  "The neo-Nazis, and the Right Sector forces with the Ukrainians, they should know that for every dead Cossack, we will send 100 of their bodies back. And not even their bodies, we will send them back in bags so not even their mothers can recognise them."  Across the region, roadblocks formerly manned by separatists are now smouldering remains of tyres and firewood after the Ukrainian army rolled through. In many places, the separatists are rebuilding their checkpoints, some manned by teenagers with crowbars or drunk men asking for money, others by armed fighters.  On the road into Slavyansk, the main stronghold of separatist feeling, a Ukrainian army checkpoint has been set up. Heavily armed soldiers make every person get out of their car for searching.  The interim Ukrainian government in Kiev has referred to the separatists as "terrorists" and its movements in the east of the country as an "anti-terrorist operation". On Saturday, interior minister Arsen Avakov said a television tower above Slavyansk had been retaken by Ukrainian forces. It had been seized several weeks ago by the protesters, who had switched over the region to Russian television channels, which paint the events in the east in a very different light to the Ukrainian channels which had broadcast previously.  On the approach to the tower on Sunday along a track lined with bullet casings, Ukrainian paratroopers held positions behind two armoured vehicles and shouted that they would shoot if approached. The Ukrainian flag was flying from the tower, and a military helicopter could be seen taking off. At a still-burning roadblock nearby, locals said that several people had died as the Ukrainian army had moved in.  Near the tower, a woman who gave her name as Lyubov Ivanovna said she had seen terrible things as the Ukrainian army had moved into the area. She heard a gun battle early on Saturday morning and ran down the hill to one of the separatist barricades to stand in the way of the armoured vehicles, holding an icon. She said she saw Ukrainian soldiers shoot at unarmed civilians and, holding back tears, said she believed that Ukraine in its current boundaries was no longer viable. "I was born in western Ukraine myself, I am a Ukrainian, I want to be part of Ukraine. But not part of this Ukraine."  On their sweep through Kramatorsk, the Ukrainian army succeeded in pushing the rebels out of the local headquarters of the SBU, the security services. But contrary to Ukrainian media reports, they had not held the building, and had instead fled.  On Sunday, the flag of the Donetsk People's Republic still flew from the roof, and the hole in the fence where a Ukrainian army vehicle had stormed the compound was visible, but the building was abandoned. Inside an eerie silence reigned; the ransacked rooms reminiscent of a museum of Soviet-era espionage. A portrait of Felix Dzerzhinsky, the founder of the Soviet secret police, overlooked contraptions for intercepting telephone calls, signs warning against drinking ("A drunk man loses his self control and can easily give away state secrets") and type-written dossiers on local dignitaries.  A sense of lawlessness permeates the region, as the police have largely melted away or joined the separatists. On Sunday evening, several thousand people marched through the streets of the regional capital wielding clubs, crowbars and bricks, tearing down Ukrainian flags from buildings on their route and smashing their way into the military prosecutor's building. There was disappointment as they realised that everyone had gone.  Amid the mood of tension and violence, there also remains disagreement within the ranks of those protesting about what their ultimate goal is: increased autonomy within Ukraine, an independent republic or absorption into Russia.  In Donetsk, as the crowd wound through the streets on the way to the military prosecutor's office, there were chants of "Russia! Russia!" and two young men spray-painted Russian flags on lamp-posts along the way.  Another group accosted them and told them that they should be spraying the red-black-blue Donetsk Republic tricolour instead of the red-white-blue Russian tricolour.  "We are for Russia!" one shouted back. "But also, we didn't have any black paint."
A week before Donetsk region votes on secession, rebels are rebuilding barricades despite Kiev's attempt to retake control