U.S. forces have stormed Fallujah, moving to retake the Iraqi city from insurgents.

Thousands of Marines and Army infantry, backed by warplanes, tanks and artillery, moved on the northern edge of the city early this (Monday) evening. Reporters say Marines and insurgents exchanged heavy fire as parts of the city burned. Arabic voices on loudspeakers urged insurgents to resist.

Iraq's interim Prime Minister Iyad Allawi gave the go-ahead for the Fallujah assault, and promised the rule of law will soon be restored.

The top U.S. commander in Iraq, Army General George Casey, said he expects a major confrontation in Fallujah. But he said the offensive is on schedule and that at least half the city's 200,000 residents left before the attack.

Early U.S. casualty reports said 42 insurgents had been killed in the attack. Two Marines were killed when their bulldozer flipped into the Euphrates river.