The Iraqi soldiers were travelling in a five-vehicle patrol near Baquba, 60km (40 miles) from Baghdad, when they were hit by a roadside bomb and then came under gunfire.

Police sources said 19 soldiers died and that they were all from southern Iraq.

The deaths come amid a rise in violence in the run-up to elections set for 15 December, and growing tensions between Iraq's Muslim sects.

In a move that could aggravate those tensions, the country's top Shia leader, Ayatollah Ali al-Sistani, has urged Shia to turn out and vote for religious candidates on election day.

Video

Aljazeera broadcast a video on Saturday from a group called the Islamic Army in Iraq showing the attack on the US patrol near Falluja on Thursday, the deadliest attack on US troops for four months.

The Islamic Army claimed responsibility for the attack that killed the 10 US marines, but the video's authenticity could not be verified.

The US military said the video did
not show the attack claimed

The video shows a Humvee, flanked by troops travelling slowly down a street, and a huge explosion engulfing the vehicle and sending bystanders fleeing.

But the US military said on Sunday that the video did not show the same incident.

"The circumstances of the IED (improvised explosive device) attack near Falluja do not match those shown on the video," the US Marine Corps said in a statement. 

"While we are unable to discern whether the video shown is authentic, the statement that the video shows the 1 December IED attack near Falluja is false." 

The deaths from Thursday's attack raise to more than 2120 the number of US troops that have died in the war. The blast also wounded 11 marines and was the largest loss suffered by US forces since August.

Fighters wired several artillery shells together, hid them and then detonated this so-called daisy-chain as a foot patrol passed by. 

More violence expected

US commanders have said they expect an increase in violence in the build-up to the election. Over the past three weeks there has been a series of car bombings and attacks in which more than 230 Iraqis, mostly civilians, have died.

Saturday's ambush on the Iraqi troops occurred in Udaim, a volatile town near Baquba, and is the latest in a series of attacks to target Iraq's fledgling police and army forces.

Sunni Arabs form the backbone of the campaign to destabilise the Shia and Kurdish-led government and drive US-led forces out of Iraq.

Some Sunni leaders have indicated their readiness to negotiate a ceasefire before the polls to encourage Sunni participation, after they boycotted the January election and ended up with only 17 seats in the 275-member parliament.