In the far west, where US marines have been fighting for months to stem a flow of foreign Arab fighters and funds from Syria, local doctors and tribal leaders accused American forces of killing some 40 civilians in an air strike.
The military said it knew of no civilian deaths and believed it had killed an al Qaeda leader targeted by precision bombing.
Two roadside bombings near Baghdad on Monday killed six soldiers and the military also announced the death of a Marine, who was killed by a similar device near Falluja on Sunday.
That made October, which saw Iraqis vote for a constitution and put Saddam Hussein on trial, the worst month the Americans have suffered since January, when violence surged in advance of a parliamentary election.
Suicide bombers, like one who lured Shia townsfolk to their deaths on Saturday with an exploding truck full of dates that killed 30, are believed often to be foreigners, brought in through Syria.
Near the border city of Qaim on Monday, US aircraft bombed a house close to Karabila before dawn in what the military said was a precision strike on an al Qaeda leader.
A local hospital doctor in the Iraqi town of Qaim said 40 people were killed and 20 wounded, many of them women and children, and a tribal leader said no guerrillas were there.
A US military spokesman said the precision bombing in Karabila, close to Qaim, was meant to avoid civilian casualties.
"We believe the targeted terrorist leader was killed but we cannot confirm that," Colonel David Lapan said.