(Updating with further details)

SAMARRA, Iraq (AFX) - Four children were killed and at least 20 people wounded in a double car bombing in the path of a US army convoy near a nursery school in the Iraqi city of Samarra, local officials said.

A US military spokeswoman said 11 US troops were among the wounded in what was the first major attack in Samarra since it was wrested from insurgents in a deadly offensive by American and Iraqi troops at the start of October.

"A pair of vehicle concealed IEDs (improvised explosive devices) detonated near the city centre in Samarra," the spokeswoman told Agence France-Presse.

In the battle-scarred city north of Baghdad, Doctor Hussein Alaeddine said four children had died and 20 people were wounded.

The casualties were evacuated to Samarra's general hospital.

Police commander Salah Hussein said it had been a car bomb attack, adding that one of the US army vehicles in the convoy had been damaged.

Residents said the US army had sealed off the area and announced a curfew in the city between 7.00 pm and 7.00 am.

The military spokeswoman said bombs had been concealed in two vehicles that exploded, killing one child and injuring 11 US troops and an Iraqi civilian.

The US-Iraqi offensive on Samarra, which the US military said claimed the lives of more than 150 people, including 20 civilians, marked the first major push to retake a Sunni rebel bastion ahead of January national elections.

In the latest operation into insurgent hotspots, US and Iraqi troops have been encircling the city of Fallujah, west of Baghdad.

str-dmh/al