The death toll in the co-ordinated suicide bomb attack on the minority Yazidi sect in northern Iraq could be as high as 500, medics have said.

The American military said that there was little hope of finding anyone still alive in the rubble of scores of houses destroyed in two remote villgers by at least four suicide bombers on Tuesday evening.

Many of the wounded and dead were children

The number of confirmed dead was 175, with more than 300 injured and 600 made homeless. But medics speculated that the real toll could be closer to 500.

Bodies covered by blankets could be seen laid in the street and outside a municipal building. Rescuers are still digging through the rubble of the bomb-flattened clay-built homes in scenes reminiscent of an earthquake zone.

But Major Rodger Lemons, operations officer for a US brigade in the area, which is near the city of Mosul, said that rescue efforts are winding down.

"My assessment is there's probably no one left alive in the rubble," he said. "We've transitioned through to a clean-up phase."

The US military has said the "al-Qa'eda in Iraq" group is the prime suspect for the attack on the Yazidis, seen by Sunni Muslim militants as infidels.

Major Lemons said it appeared that two refuse trucks packed with explosives had been driven into each of the villages, Kahtaniya and al-Jazeera.

Rescuers search rubble in Al-Qataniyah for victims of the bombs

In al-Jazeera, Iraqi security forces shot and killed the driver of one truck before it reached the village. Both trucks detonated in Kahtaniya village, he said.

The bombings could be the bloodiest co-ordinated attack in Iraq since the US-led invasion in 2003.

In November 2006, six car bombs in Baghdad's Sadr City Shia slum killed 200 people and wounded 250.

The governor of Nineveh province, Duraid Kashmoula, said the blasts in Kahtaniya and al-Jazeera had levelled hundreds of houses and buried entire families. He put the death toll at 220.

But Kifah Mohammed, director of Sinjar hospital in the area of the bombings, said the toll could be 500, with 400 wounded.

"I don't know if we'll ever get to a point where we'll have an exact figure," said Major Lemons.

Yazidis are members of a pre-Islamic Kurdish sect in northern Iraq and Syria who say they are persecuted because of their beliefs.

US officials fear that the attack in the remote area may signal the start of a new campaign against "soft targets".

These can be found away from areas where there is a major US and iraqi military presence, such as in Baghdad and Anbar province where thousands of troops are involved in operations as part of the US security "surge".