A BLACK WATCH soldier was killed and two were injured in Iraq yesterday as thousands of US troops fought their way into Fallujah.

The Ministry of Defence said there would be a full investigation into the latest attack, which takes the regiment's death toll to four in less than a week.

A spokesman said: "At 6.30pm local time, a Warrior armoured vehicle from the Black Watch battle group was hit by a roadside bomb north of Camp Dogwood.

"The Warrior left the road, its wheels destroyed on one side, and one soldier was killed and two others injured - neither seriously.

"The injured men were taken by a US helicopter medevac team to a military hospital in Baghdad and the damaged Warrior was subsequently recovered to Camp Dogwood."

The incident came the day after two bomb disposal experts from the Royal Logistic Corps and the Royal Signals were seriously injured by a suicide car bomb.

Three Black Watch soldiers were also killed last week following their controversial redeployment in the US controlled area.

Last night, a Downing Street spokesman said: "Our thoughts are with the Black Watch battle group and their families after this incident."

Earlier, Prime Minister Tony Blair, paying tribute to the Black Watch members killed in last week's incident, told the Commons that the regiment was playing a vital role in Iraq.

The latest attack on the Black Watch came as US marines launched a major onslaught on the insurgent stronghold of Fallujah.

The 850-strong Black Watch battle group was deployed to Camp Dogwood, about 15 miles south of Baghdad, to relieve US forces preparing for the Fallujah assault.

They are tasked with cutting off the "rat runs" from the city, preventing insurgents escaping and supplies getting in.

The two bomb disposal experts seriously injured on Sunday have been airlifted to a US hospital in Germany.

Last Thursday, Black Watch Private Paul Lowe, Sergeant Stuart Gray and Private Scott McArdle, all from Fife, died in a suicide attack at a vehicle checkpoint.

Followers of terrorist Abu Musab al-Zarqawi, responsible for the death of kidnapped Briton Ken Bigley, claimed responsibility for their deaths.

The suicide bomber responsible for that attack is thought to have been a white Europe-based al Qaida terrorist.

A video of the attack - which also left eight Black Watch soldiers injured and a civilian Iraqi interpreter dead - has been aired on an extremists' website.

It apparently shows images of insurgents stamping on victims' body parts at the scene.

As word spread of the video, Black Watch platoon sergeant Barry Robertson, 34, from Sunderland, said: "It's just absolutely disgusting, and a cowardly thing to do. This video shows them up for the animals they are. I don't understand how they think they are going to get public support for showing videos like that."

A military source in Iraq said: "The bomber was Caucasian. That means he could be from anywhere between Bosnia to Birmingham.

"We don't know any more because there wasn't much left of him.

"But it confirms our fears that the Black Watch are now up against foreign terrorists."

Liberal Democrat defence spokesman Paul Keetch last night called on Defence Secretary Geoff Hoon to make an urgent statement to the Commons about the ongoing role of British troops in Iraq, ahead of Mr Blair's trip to see US President George Bush in Washington later this week.

Meanwhile, US troops, backed by armour and an air barrage, began a massive assault - dubbed Operation Phantom Fury - that seeks to put an end to six months of rebel control of the Iraqi city.

As night fell, troops advanced slowly on the north-western Jolan neighbourhood, a warren of alleys where Sunni militant fighters have dug in.

Artillery, tanks and planes pounded the district's northern edge, softening the defences and attempting to set off bombs and boobytraps before troops moved in.

At the same time, another force of 4,000 troops pushed into the north-eastern Askari district, the first large-scale assault into the insurgent-held area of the city.

Iraqi Prime Minister Iyad Allawi said he gave the go-ahead for international and Iraqi forces to launch the long-awaited offensive against Fallujah, aimed at breaking the guerillas before elections in January.

Earlier, US troops surrounded the area of Fallujah General Hospital, just outside the city on the western bank of the Euphrates.

Iraqi forces swept into the hospital, blasting open doors and handcuffing patients, who were pulled into the halls in a search for gunmen.

The US military said insurgents controlling the hospital were "forcing the doctors there to release propaganda and false information".