BAGHDAD - A suicide attacker in an explosives-rigged car bombed U.S. and Iraqi forces on joint patrol Friday, killing two Americans and at least three Iraqis.

The bomber struck the convoy of humvees and Stryker vehicles in the town of Jalula, 80 miles northeast of Baghdad, not far from the Iranian border, according to Iraqi officials. The U.S. military, which confirmed the casualties, said an additional six American troops were wounded in the attack.

Although U.S. forces have largely pulled back from urban areas as Iraqis take responsibility for securing their country, Friday's attack illustrates the risks that remain for American troops here.

Names of the casualties were not released, pending notification of family members.

The U.S. military said that along with the three Iraqi deaths, about 22 others were wounded in the blast. It was the deadliest reported attack on U.S. troops since April 7, when two soldiers were killed by a roadside bomb in Mosul.

A man who was watching the patrol from his doorway when the bomber struck said he believed troops were searching for weapons after a dispute among residents brandishing hand grenades and firearms the previous day. The man, who gave his name as Abu Kowyan, said the assailant attacked from a nearby alley, ramming his car into the patrol as troops were getting out of their vehicles. The fiery explosion shattered windows in his house 20 yards away.

Iraqi officials put the death toll higher. They said the blast killed six Iraqis, including one policeman.

Jalula is in a corner of Diyala province populated by Kurds and Sunni Arabs. In March last year, a bomber struck a Kurdish funeral there, killing 27.

The number of Americans dying in Iraq has dropped sharply, in part because of reduced troop levels as U.S. combat forces prepare to leave by the end of August. But attacks continue. Friday's attack raised to at least four the number of American deaths this month.

Also Friday, a bomb hidden in a pile of trash exploded at a market in southern Baghdad, killing three people.