The bomb exploded around 9:30 a.m. A police official said one of the severed heads that was retrieved after the bombing belonged to a former member of Saddam Hussein’s ruling Baath Party.  Elsewhere, the Iraqi police near Mr. Hussein’s hometown of Tikrit said they raided a hide-out that belonged to Mr. Hussein’s former vice president, Izzat Ibrahim al-Douri, who has eluded capture for nearly five years.  Documents retrieved during the raid indicated that Mr. Douri had been there recently, the police said. The documents detailed ties to Al Qaeda in Mesopotamia, a predominantly Iraqi group that American intelligence says has foreign leadership. They also laid out Iraqi police targets and included the blueprints of Iraqi military bases, the police said. The authorities said they also found the attack plan for a Mosul jailbreak that occurred in May, when five prisoners accused of terrorism escaped and two guards were killed.  Weapons, including mortars, were also found. Mr. Douri sits at the top of the Iraqi government’s most-wanted list, and is accused by Washington of heading and financing terrorist operations here.  Outside the northern oil-rich city of Kirkuk on Friday, extremists blew up an oil pipeline with such force that people nearby said they thought they had been under missile attack. No one was killed.  Also on Friday, an official with the political party of the anti-American Shiite cleric Moktada al-Sadr lashed out at one of Mr. Sadr’s chief political rivals, Abdul Aziz al-Hakim, for his recent visit to Washington.  “America represents the tyranny in the world,” the official, Sheik Salah al-Ubaidi, said to worshipers at a mosque in the holy city of Najaf. “And visiting the head of the tyranny without justification reflects submission to the tyranny.”  Mr. Hakim, who heads the Supreme Islamic Iraqi Council, met with President Bush last week. For years, his followers engaged in bloody clashes with Mr. Sadr’s militia. Two months ago, the leaders announced a peace agreement that has been credited with driving down violence, though it is unclear how long the cease-fire will last.  A version of this article appears in print on , on Page A9 of the New York edition with the headline: Car and Suicide Bombings Kill 25 North of Baghdad. Order Reprints| Today's Paper|Subscribe
Separate attacks in the tumultuous province of Diyala hit the headquarters of former insurgents working with the U.S. and a checkpoint in Baquba.