A US air strike has killed six Iraqi civilians, wounding 15 others in the Sadr City area of Baghdad, police and witnesses say.

They said the air strike also set fire to a building, destroyed several vehicles and damaged homes.

One local woman told AP Television she was at a loss to understand why her people were being attacked.

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''Why do aircraft and missiles pound us? They destroyed our houses and our properties. Why?" Um Hussein exclaimed.

The US air strikes have left many Iraqi civilians dead and wounded since March 25 when the Mahdi Army of anti-American cleric Moqtada al-Sadr has been involved in fierce clashes with US troops and Iraqi forces after Prime Minister Nouri al-Maliki ordered a security crackdown in the southern city of Basra.

Al-Sadr points the finger of blame at US forces as the single cause of Iraq conflicts, demanding an end to the US-led occupation of Iraq and calling on the Iraqi government to back its people to rid the land of the occupiers.