One soldier from Task Force Iron Horse died and four others were wounded when a bomb exploded at about 9:40 am in the centre of Baqouba, about 35 miles northeast of Baghdad, the 4th Infantry Division said.

Two Iraqis were arrested, including one who had a mobile phone that may have been used to detonate the bomb, according to Master Sgt Robert Cargie, a division spokesman in Tikrit.

The other fatal bombing was in the centre of Baghdad about 9:20 am, killing one soldier from the 1st Armoured Division and wounding another, the military said. The 1st Armoured is due to leave Iraq in the coming weeks and be replaced by the 1st Cavalry Division.

The latest deaths bring to 540 the number of US service members that have died since the United States launched the Iraq war in March. Most have died since President George Bush declared an end to active combat on May 1.

Also on Monday, the US command said gunmen in a white sedan opened fire on Saturday on a taxi that was taking Americans from a religious group from the site of the ancient city of Babylon back to Baghdad.

The three wounded were taken to a hospital in Mahmudiyah, about 15 miles south of Baghdad, the US military said.

The statement did not identify the religious group with which the Americans were affiliated, but a number of Christian humanitarian groups are working in Iraq.