US forces responded to the attack, by opening fire and killing four attackers, our correspondent said.

"Several rockets were fired on a convoy and two jeeps and three armoured personnel carriers caught fire," witness Mohammad Hamad al-Halboussi told Agence France Presse at the scene.
 
"The attackers ran away and then came back to open fire with Kalashnikovs and pistols on the American soldiers," he added.

90 minute battle

The attack, which began at 7:00 am (0300 GMT), and the subsequent gun battle lasted about 90 minutes, in the village of Albu Alwan, seven kilometres (four miles) west of Fallujah, said Majid Ibrahim Allawi.

"I was arrested for two hours by American forces and I saw 12 (US) soldiers on the ground."

US soldiers face daily attacks

"They were driven in the direction of camp al-Habani," a former base of the Iraqi army now used by US forces.

More attacks

At 10:30 am (0630 GMT), an AFP correspondent witnessed an explosion on the road in Albu Alwan which occurred 15 metres (yards) from a US patrol, but there were no casualties.

Fallujah, a Sunni Muslim bastion 50 kilometres (30 miles) west of Baghdad, is the scene of frequent attacks on US forces occupying Iraq and relations in the town have been strained since US troops shot dead at least 16 demonstrators in April.

In a separate incident, unidentified attackers fired mortar shells at a base housing Polish troops in Hilla, a town near Baghdad.

 

Five mortar shells were fired at the base early this morning, all landing at the edge of the facility.

 

There were no casualties. US special forces gave chase, but failed to apprehend the assailants.

Gas explosion near Baiji

Saboteurs exploded part of a key gas pipeline near Baiji in northern Iraq, another Sunni dominated area of Iraq on Thursday.

Saboteurs blamed for blast.

The pipeline was ablaze Friday following a large blast overnight, police told AFP.

"It is an attack, a sabotage," said a high-ranking Baiji police officer who did not want to be identified.

"It could be the Fedayeen (militia), or supporters of the old regime, or criminals," he said.

US military helicopters were seen hovering over the fire four kilometres west of the northern Iraqi refinery town Baiji, site of strategic pipelines in Iraq's massive oil and gas sector, an Agence France Presse correspondent on the scene reported.

Witnesses said they heard an explosion on Thursday night near Baiji, around 200 kilometres north of Baghdad.

Huge reserves, crippled infrastructure

Sabotage and looting have plagued the oil and gas sectors, with pipelines suffering crippling damage, while just 150 of 700 oil wells are in working order, officials have said.

Iraq's oil reserves, the second largest in the world, are estimated at 112 billion barrels, while its gas reserves are the world's 10th largest, according to the US-led coalition occupying Iraq.

The attack heightens concerns over Iraq's capability to maintain safety and security in its lucrative fossil fuel industries.

Oil is crucial to the occupying power's plans to rebuild Iraq. The US is banking on sales of 3.4 billion dollars this year, which would supply half the six-billion-dollar state budget it announced earlier in the month.