US warplanes pounded eastern suburbs of the city of Fallujah, the backbone of the insurgency in Al-Anbar, sending columns of black smoke into the sky, said an AFP correspondent embedded with the marines.

The strikes early Monday followed fighting that killed eight marines and at least 17 suspected rebels in Al-Anbar since Friday, the US military said, without specifiying whether the marines' deaths occurred in Fallujah itself.

"Airstrikes were called in during escalation of force for troops in contact," a marine spokesman said Monday.

Seven marines assigned to the Ist Marine Expeditionary Force were killed in action in two separate operations Sunday, the marines said in a statement which gave no further details.

Another marine was killed Saturday.

The fighting erupted in Fallujah after days of relative calm following last month's blistering assault on the Sunni Muslim city by US and Iraqi troops.

Coalition troops killed hundreds of fighters during the attack, which began November 8, but have continued to face resistance, often in parts of the city they had previously cleared.

"They hole themselves up in houses and they wait for the chance to kill an American," said Lieutenant Rex McIntosh of the 3rd Battalion, 1st Marines.

McIntosh added that many of those fighters still hiding in Fallujah's ruined neighborhoods had escaped previous sweeps by the marines.

"There's a fairly effective cordon around the city but not every unit has been doing a full clearing," he said, as his unit searched Sunday house-to-house for rebels or weapons caches.

Marines from the battalion found themselves in a running battle with insurgents that began Friday and raged until Saturday.

"We had very, very heavy contact against a group -- you could call it a cell -- which was bypassed in previous sweeping operations," McIntosh said. "By the end of Saturday afternoon we counted 17 dead rebels."

The fighting marked an escalation in violence after days of relative calm, forcing the marines to call in both tanks and fighter jets.

Clashes erupted again Sunday as marines battled fighters in northeast Fallujah, according to one marine, who told AFP the area was supposed to have been cleared of insurgents.

Large explosions could be heard and flashes lit the sky Sunday night as jets were heard overhead, the correspondent said.

Marines had earlier told AFP that rebels were creeping back into previously cleared city blocks, and the military was in a race to seize weapons caches before they could be used against them.

Large numbers of weapons, mostly assault rifles and mortars, continue to be found in abandoned homes. At least 70 rifles and other weapons, including rockets and grenades, were seized by marine patrolling the city on Sunday.

US and Iraqi forces are trying to restore order in devastated Fallujah as hundreds of thousands of residents driven out by the fighting wait to return to their homes.

The marine's top commander in Iraq, Lieutenant General John Sattler, said last week he was told by Iraqi military officials that civilians might be allowed back into Fallujah at the end of December.