One US soldier was killed and four were wounded in two ambushes in Iraq on Monday.

The US military said in a statement that gunmen fired assault rifles, machineguns and rocket-propelled grenades at a convoy of the 3rd Armored Cavalry Regiment convoy near the town of Haditha, 180 km northwest of Baghdad.

"The eight-vehicle convoy was conducting a resupply mission from Al Asad Air Base to Al Qaim (on the Syrian border) when it was attacked at about 6:15 a.m. (0215 GMT)," it said.

One soldier was killed and another injured in the attack, it said.

Hours later, an explosion ripped through a US military convoy on a highway on the outskirts of Baghdad, wounding three soldiers and destroying their Humvee military car, US soldiers and Iraqi witnesses said.

"An RPG (rocket-propelled grenade) could not have done this… it must have been a landmine," said a US soldier who was travelling in the convoy. An officer said soldiers saw a grenade being hurled at the vehicle.

The convoy was travelling on Amiriyah highway in western Baghdad. US troops, backed by tanks, sealed off the scene.