"What we have for battle damage assessment right now is essentially a hole in the ground, a site of destruction where we wanted it to be, where we believe high value targets were," Major General Stanley McChrystal, vice director of operations of the Joint Staff, told a press conference.

"We do not have a hard and fast assessment of what individual or individuals were on site," he said.

Witnesses reported that at least 14 civilians were killed in the bombing that destroyed four houses and left a crater eight meters (26 feet) deep and 15 meters wide.

McChrystal said the Iraqi Republican Guards in the capital were still receiving orders, but were not following them, or were incapable of carrying them out.

Tank-backed US troops meanwhile battled for control of Baghdad, and three journalists were killed in separate US strikes.

Cameramen from the Reuters news agency and Spanish televison station Telecinco were killed when a US tank fired on the Palestine Hotel, where foreign journalists have been staying.

The US military said the tank had fired a single round at the hotel in response to grenade and small arms fire from the building. Journalists there at the time denied gunfire had come from the building.

And a correspondent for the Al-Jazeera Arabic television network died after the station's offices were hit in a separate attack that the Qatar-based network said was a deliberate US strike, which the US military denied.

The Iraqi capital was virtually surrounded and US Army forces fanned out further in the city while Marines in thousands of armoured vehicles poured in from the east after clearing road jams at a key bridge crossing.

"Elements of the 1st Marine Division crossed the Diyala river and will link up with the 3rd Infantry Division today," said Lieutenant Colonel Ted Ohnemus.

Clearing the bridge across the Diyala, which runs east of the Iraqi capital, "caused a delay of a couple of days," said Ohnemus, a liaison officer with the First Marine Expeditionary Force.

He said there was "probably a few kilometres, it's not very much" of an area that had still not been sealed.

The marines overcame the obstacle by apparently using their own bridge, he added.

Ohnemus said the 269 Battalion of the 3rd Brigade Combat Team "will link with the 3rd Battalion of the 7th Marines" to close the circle around Baghdad.

Fresh waves of airstrikes pounded the southern and southeastern fringes of the city, while in the centre, two US tanks captured a key bridge over the river Tigris, where they met stiff resistance from Iraqi forces.

But Iraqi Information Minister Mohammad Said al-Sahhaf remained defiant, telling journalists US forces would surrender "or be burned in their tanks."

Hundreds of families fled the intensive bombing, driving eastwards in cars, trucks and minibuses overflowing with mattresses, kitchen utensils, beds and food, AFP correspondents reported.

"I'm closing the house and leaving with my family for a safer place. I will come back every now and then to see if something happened," said Ali Rishek, 53, before driving away with his wife and their three children.

The chief of staff of British forces in the Gulf warned of a potential "final act of defiance" by Saddam, with the collapse of his regime looking "inevitable."

"There is always the possibility that they were able to organise some final act of defiance -- and we've got to keep on our guard against that," said Major General Peter Wall.

Baghdad took on the appearance of a ghost town later in the day, plunged into darkness by a power cut, with sporadic explosions heard from the southern rim of the city.

US President George W. Bush, meeting chief ally British Prime Minister Tony Blair in Belfast, reiterated that US forces did not know if Saddam was dead or alive after Monday's targeted bombing.

"I don't know whether he survived ... The only thing I know is that he is losing power... Saddam Hussein will be gone," Bush said after his third meeting with Blair in as many weeks.

With focus shifting to a post-war Iraq, Bush pledged that the United Nations would have a "vital role" to play in rebuilding the shattered country, denying a reported split over the UN's role in supervising an interim Iraqi government.

Britain wants the United Nations to oversee any interim Iraqi military administration while Washington has sought initial US-British military control.

French Foreign Minister Dominique de Villepin expressed satisfaction at the statement on the UN's role.

"France is of course pleased at the stance that has been taken by President Bush and Prime Minister Blair," he told reporters.

In London, Iraqi opposition groups said they would meet in the southern Iraqi city of Nasiriyah on Saturday to discuss the country's future.

One US Marine was killed and six others wounded in firefights in the Baghdad suburbs, hours after they had completed their final advance into the capital, military officials said.

A US commander said that an A-10 Thunderbolt strike aircraft was shot down over Baghdad and crashed, but the pilot ejected and was rescued.

In southern Iraq, a spokesman for British forces said "a couple more days" were needed before Iraq's second city of Basra could be declared secure, a day after Britain had said the battle for the city was largely over.

While some Basra residents defaced murals of Saddam after the British entered, thousands looted public buildings and homes of Baath party members.

But one Basra resident told AFP: "The people in Basra feel defeated. Sure, we certainly hated Saddam but we also hate the British and Americans."

British spokesman Colonel Chris Vernon said that senior officers had met with an unidentified Iraqi leader to draw up an interim committee to run the city after the collapse of Saddam's Baath party in the city.

In London, a government minister said British forces were holding more than 6,500 Iraqi prisoners of war.

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