Members of the 3rd Infantry Division shot at the van, which was carrying 13 civilian passengers, as it approached a checkpoint and refused to stop on its way out of the city.

US soldiers indicated at the vehicle to stop, at about 4.30pm local time (2.30pm BST), US central command said. When it did not do so they fired warning shots, before shooting first at the engine and then at the passenger compartment.

Today's incident follows the death of four US soldiers on Saturday, when an Iraqi claiming to be a taxi driver carried out a suicide bombing at a Najaf checkpoint.

US troops in battle for key river town

Earlier in the day, 35 Iraqi troops were reported to have been killed as US forces fought to gain control of a key bridge over the Euphrates river at Hindiya, between Kerbala and Hilla.

The casualties were reported after coalition soldiers engaged in fierce street fighting with Iraqi paramilitaries and claimed to have captured dozens of members of Saddam Hussein's Republican Guard.

US soldiers this evening claimed to have taken control of the town centre, which is about 50 miles south of Baghdad, but were still under fire from Iraqi forces on the eastern side of the river.

Captured Iraqi troops bore the triangular insignia of the guard's Nebuchadnezzar Brigade, based in Saddam's home area of Tikrit in northern Iraq.

This led defence officials to believe the Iraqi military has sent reinforcements from the north. A week of heavy bombing has left some of Iraq's Republican Guard units surrounding Baghdad at less than half strength, with the Medina and Baghdad divisions the most severely degraded, Pentagon officials said.

Further south, intense fighting continued during the day around the Shia Muslim holy city of Najaf as US forces advanced on the city. About 100 Iraqi paramilitary fighters were reported to have been killed, about 50 Iraqis captured and US soldier killed, US Central Command said.

More bombs strike Baghdad

US bombers tonight targeted government buildings and army positions on the outskirts of Baghdad while just before 11 pm local time, (2100BST), at least five huge explosions rocked central Baghdad; at least two coming from the area of a presidential complex used by Saddam Hussein, Reuters reported.

"A big, big, big cloud of smoke is coming out of the compound. Maybe they are using bigger bombs than before," said Reuters correspondent Samia Nakhoul.

The headquarters of the Iraqi Olympic Committee, headed by Saddam's eldest son Uday, was also hit and was reported to be ablaze.

Earlier this evening, intense artillery fire was heard to the south of the city, where Republican Guard units are encamped.

In the now almost continuous air raids, bombs twice struck the palace of Saddam Hussein's son, Qusay, earlier today and are also reported to have hit the headquarters of the Iraqi Olympic committee, headed by Qusay's older brother, Uday.

Two direct hits were registered on the central telephone exchange, flattening the six-storey building while other exchanges were also struck, knocking out nearly all of Baghdad's telephone lines.

Air raids that targeted the ministry of information appeared to have successfully knocked out Iraqi national TV this morning. Broadcasting resumed after midday, four hours later than usual.

There were also reports of heavy bombing in Kirkuk and Mosul.

The US president, George Bush, today gave an upbeat assessment of progress in the war on Iraq, claiming that coalition forces now had control of most of southern and western Iraq and had achieved almost complete air superiority.

"Day by day we are moving closer to Baghdad; day by day we are moving closer to victory", the president said.

Four US marines killed in tank incident

A US tank plunged from a bridge into the Euphrates river last week in an incident in which all four crew died, US military officials announced today.

The driver was shot dead while driving over a bridge near Nassiriya on Thursday, apparently causing the accident in which the other three marines inside the tank drowned.

The tank and the dead marines were not pulled from the river until yesterday, US Central Command said. The incident occurred during a heavy sandstorm, Centcomm added.

Red Cross visits Iraqi PoWs

The International Committee of the Red Cross (ICRC) today said it had started visiting Iraqi PoWs held by coalition forces prisoners near the southern town of Umm Qasr.

The ICRC's Middle East chief, Balthasar Staehelin, said 15 members of the organisation had visited the camp, registering about 100 prisoners and inspecting the facilities. According to Britain, about 8,000 prisoners of war have been taken since the war began 12 days ago.

As yet no arrangements have been made for the ICRC to visit coalition PoWs held by Iraq.

The ICRC is guaranteed access to PoWs by the 1949 Geneva conventions, which both sides have signed. The ICRC said it is actively engaged in dialogue with the Iraqi authorities over PoW visits, and is "hopeful" that a date will soon be set.

Seventeen US soldiers are missing in action; among them seven are known to have been captured by Iraqi forces.

US: Iraqi PoWs will not be sent to Guantanamo

The ICRC visit comes as US central command today rebutted reports that American forces have been rounding up Iraqis suspected of paramilitary activity and may ship them to Guantanamo Bay.

In a military briefing at central command in Qatar, US Brigadier General Vincent Brooks said: "Right now at this point, we are treating all that we have taken into our custody as prisoners of war."

Iraqi paramilitary forces that acted as death squads and carried out "brutal acts" against civilians would be held accountable under the Geneva conventions, he added.

Brig Gen Brooks said that no decision had been made to designate any of the more than 4,000 Iraqi prisoners as unlawful combatants and send them to the Guantanamo Bay prison camp - where alleged "unlawful combatants" from the Afghanistan war are still being held.

A report in the Washington Post said that military lawyers were drafting criteria designed to guide front-line troops on how suspected paramilitary Iraqis could be taken into custody.

Brig Gen Brooks added that US special forces are now in control of movement across Iraq's western desert.

"We are denying freedom of movement throughout the western desert and are being very effective at it," he said.

Baghdad refugees arriving in Jordan today said they passed through a US checkpoint halfway along the motorway through the western desert. According to the US, two airfields in the western desert were seized by US forces in the early stages of the war. Analysts described them as useful "staging posts" for troops and supplies in the push for Baghdad.

Fresh water pumped to southern Iraq

British troops today began pumping water to southern Iraq, in a rare piece of good news for its beleaguered residents.

Just over the Iraqi border In Kuwait, the country's chief humanitarian official, retired general Ali al-Mumin, presided as water was piped into Iraqi trucks from heavy plastic pipes.

"At the moment this is the only guaranteed potable water supply in southern Iraq," said a British military official, Major Hugh Ward.

He said the pipe would supply 2m litres a day - enough for more than a quarter of a million people. The water would only be trucked to areas under secure control where 100,000 people live, including Umm Qasr and nearby town of Umm Khayy.

American journalist fired over Iraqi TV interview

NBC has fired the Pulitzer prize-winning reporter, Peter Arnett, after he gave a controversial interview to Iraqi state television in which he said American military plans had failed.

Arnett has already apologised for the interview, which he described as a "misjudgment".
Full story: Arnett fired by NBC after Iraqi TV outburst

Powell to fly to Turkey for talks

Meanwhile it was announced today that the US secretary of state, Colin Powell, will depart tomorrow for diplomatic visits to the Turkish capital, Ankara, and Brussels, where Nato's headquarters is based. Mr Powell will be discussing relations between Nato and Turkey, a US official said.

US-Turkish relations are still strained following the refusal of Turkish MPs to pass a deal, worth billions of dollars, allowing US troops to invade Iraq through Turkey.

Royal Marines continue 'Operation James'

British commandos today arrested five people during a raid on a Ba'ath party headquarters just south of Basra. They also destroyed Iraqi tanks and seized equipment in the Basra suburb of Abu al-Khasib, secured after a full day of fighting yesterday.

A Royal Marine was killed and the Iraqis suffered a "large number of casualties" in yesterday's battle for the village, a British commander said.

The troops, from 40 Commando, are spearheading the British push for the southern city of Basra, named 'Operation James' after the James Bond spy films. Now around a mile from Basra, they attacked two enemy positions today, dubbed 'Pussy' and 'Galore' by military commanders.

Hoon: no senior Iraqis have defected

No senior Iraqi politicians or soldiers have defected since the conflict began 12 days ago, according to the defence secretary, Geoff Hoon.

"There have been, as yet, no defections of very senior politicians or very senior military commanders, but that is certainly not to say there have not been significant surrenders," Mr Hoon told MPs today.

"We currently hold around 8,000 prisoners of war, many of whom in fact have surrendered and many of whom were pleased to surrender," he said.

Mr Hoon also appeared to rule out the possibility of sending significant British reinforcements to join the war effort.

"What I am ruling out, at this stage anyway, is the necessity of any substantial increase of our troops," he said. However, he did say that the TA and other reservists "could be called on to provide assistance".

Mr Hoon's words come just days after the first wave of US troop reinforcements arrived in Kuwait.

Faced with stronger than expected opposition from Iraqi soldiers, setbacks including friendly fire and civilian deaths, and growing unrest in the Arab world, the chief US architects of the invasion have been forced to defend their plans and send in around 100,000 additional soldiers.