Baghdad braced for the assault

,000 Iraqis killed in incursion, says US; Capital encircled by Allied troops; Three Britons die in push for Basra

Allied forces encircled and isolated Baghdad last night, launching mortar, artillery and air strikes to prepare the decisive battle to topple Saddam Hussein's regime.

An assault on Basra, by thousands of British infantry and marines, left most of Iraq's second city under their control last night, but at the cost of three British soldiers' lives.

The first American aircraft, a Hercules C-130 transporter, landed at Baghdad airport, and there was an indication of what might be to come when the US said that between 2,000 and 3,000 Iraqis had been killed in the three-hour incursion into the city on Saturday, by the 3rd Infantry Division and two squadrons of tanks.

American troops claimed to have cut off most approaches to the city. Only one main road, Route 2, which leads north to Kirkuk, remained to be secured.

On Baghdad's southern outskirts, US infantry fought in close combat with Iraqi defenders wearing red headbands with Allahu Akbar written across the front, the traditional insignia of a suicide fighter or self-described martyr.

Pressure on President Saddam had already intensified severely yesterday after British forces swept into the heart of Basra for the first time. About 2,000 troops and between 30 and 40 tanks from the 7th Armoured Brigade ­ the Desert Rats ­ backed by Royal Marines, closed in from three directions on the dense and potentially most hostile central sector of the city.

The Desert Rats' commander, Brigadier Graham Binns, said: "Their days are limited. Our intelligence tells us that morale is low among the defenders of the city, that the population can't wait to see us, and the opposition, such as it is, is uncoordinated."

Checkpoints were set up by British forces inside the city and citizens began looting as the British arrived, apparently in the belief that the regime's grip was being terminally loosened.

In the worst "friendly-fire" tragedy of the war, a US F-15E Strike Eagle attacked a convoy of US and Kurdish forces 30 miles south of Mosul, killing at least 18 people. Three American special forces soldiers died and five were wounded. The BBC world affairs editor, John Simpson, who was in the convoy, said he was saved only by his flak jacket, which was hit by shrapnel.

Artillery exchanges and mortar fire were audible in central Baghdad from the east and south-west, where 7,000 troops were massed at the airport. Firing could also be heard in central Baghdad from the east where US Marine units were reported to be massing.

The 1st Marine Expeditionary Force was also reported to be fighting for control of a road bridge over the river Tigris on the south-eastern outskirts of the city.

Military sources confirmed that one British soldier was killed in the advance on Basra ­ reportedly by a booby trap. Next-of-kin were being informed of the other two deaths.

It remained uncertain how many Iraqi deaths there had been in sporadic fighting with irregular forces and remnants of Republican Guard divisions, using mortars and rocket-propelled grenades. Last night, British troops were conducting a room-by-room search of the apparently deserted Baath Party headquarters in the city.

Military sources said that pro-regime forces numbering anything between 500 and 1,500 were thought to be offering resistance, many of them concentrated in the dense mixture of residential and industrial buildings in the Ashsmar and Mazlaq districts bordering the river, as well as in the old city.

Group Captain Al Lockwood, a British military spokesman at US Central Command, said: "We're on the edge of Basra old city now. We're in there with tanks, we're staying and we're not just going in and coming out again."

In the main tank advance, the Royal Scots Dragoon Guards rolled towards old Basra from the south-west; the Royal Regiment of Fusiliers occupied the central north-western sector of the city, and contingents of the Black Watch converged on the centre. Units from 3 Commando moved up from the south-east towards the Nahl al-Karwah canal.

A convoy carrying Russia's ambassador and other diplomats from Baghdad reportedly came under attack, and four or five people were wounded. The US military said the area was under Iraqi control, but a Russian general said the shooting came from the US side.

Earlier, asked about the Iraqi death toll in Baghdad on Saturday, US Brigadier General Vincent Brooks said it could be of the "order of 2,000". He also said that US Marines had raided a training camp near Salman Pak, where there has been a suspected but unconfirmed, biochemical weapons plant. The tip-off for the raid had come from captured Egyptian and Sudanese prisoners fighting for the Iraqi regime. Brigadier General Brooks said: "We believe this camp had been used to train these foreign fighters in terror tactics."