"We have seized a foothold. US troops control about a third of the airport," Captain Michael McKinnon of the 1st Brigade of the 3rd Infantry Division told an AFP correspondent at the airport early Friday.

US planes were continuing to bombard the airport amid Iraqi anti-aircraft fire, but fighting on the ground appeared to have stopped, with only sporadic gunfire being heard, McKinnon said.

Witnesses reported earlier that the airport had come under heavy artillery fire on Thursday, leaving dozens killed and injured.

In Washington, US Defense Secretary Donald Rumsfeld said the US-led forces were "closing in on Baghdad."

"They are closer to the center of the Iraqi capital capital than many American commuters are to their downtown offices," he said at a Pentagon news conference.

US officers at Saddam aiport said coalition troops had met little resistance. But they came under rocket-propelled grenade and mortar attacks as they made their push towards the strategic facility Thursday, said an AFP correspondent travelling with them.

More than 1,000 US troops from the 1st Brigade were active in and around the airport, US officers said, but had not taken the terminal or any other buildings in the airport.

The first US Bradley fighting vehicles and M1 Abrams tanks breached the the airport perimeter walls at 7:30 pm (1630 GMT), McKinnon said. He gave no details of US or Iraqi casualties.

US Air Force F-15E and F18 fighter jets dropped JDAMs (Direct Attack Munitions, or smart bombs) as the 1st Brigade attacked the airport from the ground, said Master Sergeant Russ Carpenter, an air force liaison officer on the scene.

The air strikes hit "at least 40, and that's a conservative estimate" Iraqi armoured personnel carriers, artillery pieces and tanks, Carpenter said, adding that they also hit Iraqi anti-aircraft guns but did not take all of them out.

US military sources said positions of Saddam Hussein's crack Republican Guard troops inside the airport had been bombed.

Airplanes have neither landed nor taken off at Saddam International Airport since March 19, a day before the launch of the US-led war on Iraq. Baghdad has a second, more central, airport, which is used by the military.

Baghdad was facing another night of coalition attacks, with several large explosions heard in the city centre at 2:30 am Friday (2230 GMT Thursday) as warplanes flew overhead, an AFP correspondent said.

US troops were within 15 kilometers (nine miles) of downtown Baghdad and controlled the southern approaches to the capital, said Major General Buford Blount, commander of the 20,000-strong 3rd infantry division.

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