Allied troops were last night within striking distance of Baghdad after destroying an entire Republican Guard Division.

They also moved across the "red line", which Allied commanders have always identified as the point likely to trigger the use of chemical weapons by Saddam Hussein's regime.

According to some reports, the Allied forces, advancing in a two-pronged formation, were within 20 miles of the Iraqi capital.

The Republican Guard's Baghdad division, up to 15,000-strong and one of six divisions defending the city, was wiped out near Kut to the south-east of the capital.

That allowed the US 1st Marine Expeditionary Force to cross the Tigris river, opening the way for the final ground assault on Baghdad.

To the west, around the holy city of Karbala, 50 miles south of Baghdad, the US 3rd Infantry Division fought bloody street-to-street skirmishes with the Republican Guard's Medina Divison, the strength of which has been reduced by half.

The Medina, who were also bombarded by warplanes, were being reinforced from the Al-Nida and Nebuchadnezzar divisions further north.

But a military source said: "They are in deep trouble. This is the end game."

The Allied assault on the Republican Guard included a devastating aerial bombardment in which, for the first time, B-52s dropped a new type of precision-guided 1,000lb cluster bomb.

Six CBU-105 bombs were dropped, each releasing ten armour destroying "bomb-lets", which descended by parachute on to an Iraqi tank column.

Brigadier General Vince Brooks, speaking at Central Command in Qatar, said: "The Republican Guard are in trouble, they are under serious attack right now and they will continue to be until we are finished.

"The dagger is clearly pointed at the heart of the regime and will continue to be until the regime is gone.

"We are having fights and we are winning those fights as we go along."

General Brooks also revealed that British forces patrolling southern Iraq had captured five anti-ship missiles, which could also have been fired into Kuwait. They were found near Zubayr airport.

They also found plans for Iraqi artillery positions being carried by a motorcycle courier and had consequently destroyed the positions.

They remained firmly in control of the northern approach to the second city of Basra, he said.

US troops had seized a dam at Haditha, north-west of Baghdad, which could have been used by Saddam to flood the Euphrates river leading down towards Baghdad.

Elsewhere, the US 5th Corps attacked paramilitary forces in Najaf.

The paramilitaries set up base and fired from the Ali Mosque - one of the most important religious shrines to all of Shia Muslims.

Allied forces said they were not returning fire on the mosque out of respect for the Muslim religion and they described the Iraqi tactics as "despicable".

In the UK, Prime Minister Tony Blair accused Saddam of planning to wreck holy sites in Iraq and then pin the blame on coalition forces.

The Prime Minister said intelligence reports showed the Iraqi regime "intends to damage the holy sites, the religious sites, with a view to blaming the coalition falsely for that damage."

Sky News's Colin Brazier, who used to work for The Northern Echo, was with the US 3rd Infantry Division at Karbala. He said: "The commanders have built up such a head of steam they are probably going to press home their advantage."

At Central Command, Allied officials said they were investigating reports that a Red Cross maternity hospital in Bagdhad was bombed, killing several people.

There were also investigations into reports that civilians were killed in a cluster bomb attack at Hillah and that a civilian was injured when an Apache helicopter fired on his vehicle.

* Helen Guy, the pregnant wife of the region's first serviceman to die in the war with Iraq, was due to give birth to their second child last night. Her captain busband, Philip, of Skipton, North Yorkshire, was among 12 servicemen who died when a helicopter crashed.

* A BBC cameraman was killed in northern Iraq yesterday when he stood on a landmine as he climbed out of his car. Pulitzer prize-winning photographer Kaveh Gole-stan, 52, an Iranian, was filming at Kifri.

Producer Stuart Hughes, 31, was caught in the blast and injured his foot, while correspondent Jim Muir and a translator were unhurt.