The Americans were killed in a combat explosion in Diyala province north of Baghdad. Twelve others had minor injuries and returned to duty. A military statement announcing the deaths gave no other details and said identities of the victims would be withheld until family could be notified.

Earlier yesterday the military said one soldier was killed during fighting in eastern Baghdad on Monday. Two soldiers were wounded in the fighting.

The incidents mean that at least 3,674 members of the US military have died since the Iraq war started in March 2003, according to an Associated Press count. The figure includes seven military civilians.

Meanwhile, in a village in the north of Iraq, a suicide bomber blew up a truck packed with explosives, unleashing a huge blast that killed 30 people and destroyed a number of homes.

The bomber delivered the deadly attack after driving across farmland to Al-Quba. Five women were among the dead and 14 people were in a critical condition in hospital. The police said that 50 people were wounded.

The mayor of nearby Tal Afar, Major General Najim Abdullah, added: "It was filled with a massive amount of explosives. Twenty houses were destroyed, 10 of them entirely wiped out."

Sectarian fighting in other areas claimed the lives of at least 15 Iraqis.