Officers with the US Army's 3rd Infantry Division said the driver of a taxicab blew himself up at a roadblock north of the city of Najaf, where American forces were massing for a decisive push toward Baghdad.

It was the first confirmed suicide attack of the 10-day-old war that has seen US-led forces seeking to topple Iraqi leader Saddam Hussein struggle with guerrilla tactics and ambushes by Iraqi troops disguised as civilians.

Captain Andrew Valles said a man drove up to the checkpoint outside Najaf, a Shiite Muslim holy city 160 kilometers (100 miles) south of Baghdad, and waved his hand "indicating he needed some help."

Five soldiers moved toward the car. Two trained their rifles on the rear of the vehicle, two on the front and the fifth approached the driver's side.

"As they aproached the car ... he set off the bomb," said Valles, of the division's First Brigade.

A military spokeswoman at US forward command headquaters in Doha, Qatar later confirmed the car bombing but provided no casualty figures.

"We can confirm there was a car bomb explosion at a US checkpoint in Iraq early this morning outside An-Najaf," Major Randi Steffy said.

A short while later, Iraq's chief Muslim cleric pronounced a fatwa, or religious decree, calling on the people to fight against the US and British forces that have invaded the country.

The attack came as US forces stepped up the pressure on Iraqi troops defending the approaches to Baghdad, sending the vaunted 101st Airborne Division and their Apache attack helicopters into action for the first time.

As the US ground offensive hit a lull for regrouping and resupply on its 10th day, the "Screaming Eagles" of the 101st Airborne struck late Friday at Iraqi positions near the Shiite Muslim holy city of Karbala north of Najaf.

Colonel Greg Gass, the 101st's Aviation Brigade commander, said the tank-busting Apaches joined with US and British warplanes in the assault near the city about 80 kilometres (50 miles) southwest of Baghdad.

The armored Medina Division of Iraq's elite Republican Guard was reported lying in wait around Karbala, guarding the western approaches to Baghdad with an arsenal said to include more than 200 Russian T-72 tanks.

Officials have said US forces are intent on softening up the Republican Guard ahead of an expected push by the US Army's 3rd Infantry Division, which is just south of Karbala.

British Royal Air Force pilots said that laser-guided bombs and Maverick missiles took out some of the Medina Divisions's biggest guns.

Flight Lieutenant Scott Morley, a Harrier pilot, said he joined a queue of coalition planes including A10 tankbusters and American F16 and F18s to take his turn to bomb the division.

"There was fantastic visibility and I could even see the camels on the ground as well as a number of bomb craters around the encampment," he said.

"It is not carpet-bombing, it is still precision stuff. I got two good hits on Medina Division artillery pieces."

US warplanes pressed their attacks on the capital, which came under heavy bombing early Saturday, with at least one missile crashing into the information ministry.

The new attacks followed a major blow to the coalition's global public relations battle when at least 30 people were killed and 47 wounded in an air raid on a market Friday during the fiercest day of strikes since the war began.

Fierce Iraqi opposition in the south, sandstorms and long, vulnerable supply lines have prompted US commanders to put the brakes on their ground offensive while preparing to send in another 120,000 troops on top of the current 90,000.

US officials said four marines went missing during a "combat operation" in Nasiriyah in the south. A US soldier was killed and five others injured in central Iraq Saturday when their Bradley fighting vehicle rolled over.

A British soldier was missing and presumed dead and four others were injured in an apparent friendly fire incident in Iraq, the fifth such death since the war began, the British defense ministry said Saturday.

Britain's Press Association (PA), quoting a senior defense official, reported earlier that a soldier was killed after an American A10 tankbuster plane targeted two armored vehicles near the southern port city of Basra.

A total of 23 British soldiers have died in the conflict so far, including 14 as a result of helicopter accidents and four killed in action. That toll already exceeds that of the 1991 Gulf war by five.

The suicide bombing brought the US death toll to 34. The Pentagon said earlier that 104 Americans were wounded in action, 16 were missing and seven were prisoners of war, it said.

The Iraqis also left a calling card for US ally Kuwait, hitting Kuwait City for the first time Saturday.

Two people were injured slightly by the missile, which landed off the coast but caused substantial damage to one of the emirate's largest and most popular shopping malls -- Souk Sharq.

British troops, meanwhile, kept up their siege of the southern port of Basra and said they were looking out partcularly for members of Iraq's ruling Baath party.

"The targeting and eradication of the Baath party within Basra province is now our primary focus and military main effort," Colonel Chris Vernon, a British military spokesman, said in Kuwait City.

WAR.WIRE