Major General Stanley McChrystal, of the U.S. Joint Chiefs of Staff, said the status of the four Republican Guard divisions was "very confused".

"We know they have moved parts of those divisions around and in fact they have become intermixed with other elements on the battlefield," McChrystal told a Pentagon news briefing.

"We know that overall each of those remaining four divisions have been significantly attrited to this point, significantly degraded," he said.

"Those remaining four are nothing like they were when they started the battle."

The other two divisions, the Medina and Baghdad division, which formed the main defensive line south of Baghdad were missing "essentially in their entirety," claimed McCrystal.

Southeast of Baghdad, a U.S. Marine officer told Reuters correspondent the Nidaa division of the Republican Guard had "ceased to exist as an effective fighting force."

A U.S. spokesman claimed earlier that about 2,500 from Baghdad Division of the Republican Guards had surrendered to U.S. Marines who clashed with Iraqi Republican Guard forces as they advanced north on Baghdad from the town of Al-Kut.

"There are reports of 2,500 Iraqi troops who surrendered between Al-Kut and Baghdad," Navy Captain Frank Thorp told a briefing at U.S. Central Command's forward planning base.

"This is the First Marine Expeditionary Force taking on the Baghdad Division of Republican Guards."

Members of the Iraqi Republican Guard gather on the outskirts of Baghdad

He said units from the U.S. Army's Fifth Corps as well as the First Marine Expeditionary Force were "continuing to move toward the vicinity of Baghdad," in stronger numbers than on Thursday, April 3.

Separately, military sources said that three Americans were killed in fighting for the International Saddam Airport and four were wounded.

Iraq said its forces had destroyed 11 U.S. tanks and eight armored personnel carriers during fighting at the airport, adding battles were still going on.

U.S. commanders said there was no sign of threatened "non-conventional" actions by Iraq against the airport on Friday night.

U.S. commanders said hundreds of U.S. soldiers would reinforce the airport overnight.

In the meanwhile, a U.S. Defense Department spokesman alleged that Iraqi forces were hiding arms and missiles in schools and hospitals.

"We continue to see the enemy putting military assets in and around schools, hospitals, mosques, homes, embassies, clearly hoping to blame any civilian deaths on coalition forces," the spokeswoman, Victoria Clarke, told a Pentagon news briefing.

"The regime we are ousting clearly would do just about anything to hold onto power and abuse its people," she claimed.

She said that in "literally dozens of classrooms coalition troops continue to find mortar rounds, rocket-propelled grenades, anti-personnel mines and anti-tank mines."

"As we near the end of the regime," said Clarke, "we have to remember and underscore repeatedly that the very toughest fighting could lie ahead.

"It's quite possible that what's left of the Iraqi regime will continue or even escalate their horrible tactics of using civilians as hostages and shields for their own protection," she said.

More Missile Attacks

Also Friday, a missile slammed into central Baghdad at 10:45 pm (1845 GMT) Friday, shortly after a plane overflew the capital and drew heavy anti-aircraft fire.

Smoke was seen billowing in the sky but it was not clear where exactly the missile crashed.

The missile landed in the heart of Baghdad minutes after the capital's southeastern suburbs came under intensive bombing, sending red streaks into the night sky.