The violence came a day after gunmen ambushed a bus carrying unarmed Iraqis to work at a U.S. ammo dump near Tikrit, killing 17 and raising the death toll from three days of intensified insurgent attacks to at least 70 Iraqis.
The attacks, focused in Baghdad and several cities to the north, appeared to be aimed at scaring off those who cooperate with the American military — whether police, national guardsmen, or ordinary people just looking for a paycheck.
They also have targeted Kurdish militiamen and Shiite worshippers in a possible bid to foment sectarian and ethnic unrest.
In other developments:
The latest fighting in Baghdad broke out after armed rebels appeared on the busy Haifa Street, saying they were hunting for Iraqis collaborating with U.S.-led forces.
Witnesses said they shot and killed a man they claimed was working for the Americans. Rebels also were seen on a square just three blocks from the heavily fortified Green Zone that houses Iraq's interim government and the U.S. Embassy.
The U.S. military had no immediate comment, but witnesses said U.S. troops supported by armored vehicles attacked the gunmen.
Haifa Street, a thoroughfare running through central Baghdad, has been the scene of frequent clashes between U.S. troops and resistance fighters.
Sunday's bloodshed began when gunmen opened fire at the bus as it dropped off Iraqis employed by coalition forces at a weapons dump in Tikrit, 80 miles north of Baghdad, said Capt. Bill Coppernoll, spokesman for the Tikrit-based U.S. 1st Infantry Division. Coppernoll said 17 people died and 13 were wounded in the attack.
Survivors said about seven guerrillas were involved, emptying their clips into the bus before fleeing. The bodies of the victims were brought to a morgue too small to hold them all; some were left in the street.
About an hour later, a suicide car bomber drove into an Iraqi National Guard checkpoint in Beiji, 75 miles to the north, detonating his explosives-packed vehicle, Coppernoll said. Gunmen then opened fire on the position. Three guardsmen, including a company commander, were killed and 18 wounded, Coppernoll said.
Also Sunday, guerrillas ambushed a joint Iraqi-coalition patrol in Latifiyah, south of Baghdad, and attacked Iraqi National Guardsmen patrolling near Samarra, north of Baghdad. Two Iraqis were killed and 10 wounded.
The attacks followed assaults Friday and Saturday that saw insurgents hit a police station, killing 16 men, car bomb a Shiite mosque, killing 14, and car bomb a bus carrying Kurdish militiamen, killing at least seven.
Jordanian terrorist Abu Musab al-Zarqawi's group, al Qaeda in Iraq, claimed responsibility for several attacks Friday and Saturday. On Sunday, another militant group, Jaish Mohammed — Arabic for the Mohammed Army — issued a statement saying its fighters were lying low for "a few days" but planned more attacks against U.S. forces.
The group's statement, which could not be immediately verified, also warned Iraqis against aiding coalition forces and said they would be attacked with similar fury as that directed against the U.S. military.
The latest attacks on Iraqis cooperating with the interim government have been particularly brutal in their scale and have taken on a new urgency in light of the approaching vote.
While Iraq's majority Shiites are eagerly awaiting the election, the Sunnis oppose it, partly because the violence has been heavy in their areas west and north of Baghdad and voter registration there has not begun. About 40 small, mostly Sunni political parties met Sunday to demand the elections be postponed by six months, but stopped short of calling for a boycott.
President Bush, Iraqi Prime Minister Ayad Allawi and Iraq's Sunni president, Ghazi al-Yawer, have insisted the vote will be held as scheduled.