A suicide car bomb exploded outside a residential complex belonging to a state-run oil company north of Baghdad on Tuesday, killing 22 people and wounding 80, police, local hospital officials and the US military said. Local authorities said that victims were still being pulled from the rubble of two destroyed buildings and that the death toll was expected to rise. The bomber, who was driving a pickup truck, detonated his explosives when Iraqi police and members of a volunteer security force prevented him from entering the gate of the compound belonging to the state-run North Oil Company in Beiji, about 250 kilometers north of Baghdad, a police officer said. He said some of the residential buildings were damaged in the blast. Most of the 22 killed were civilians, and at least three were children, the police officer said. The dead also included guards of the oil company and members of the volunteer force. An official at the main hospital in Beiji gave the same casualty figures and said 50 were wounded. Both officials spoke on condition of anonymity because they were not authorized to release information to the media. The US military said in a statement that 20 people were killed and 80 wounded. The reason for the discrepancy in casualty figures was not immediately clear. Authorities imposed a curfew on the city - home to the country's largest refinery - until further notice. Volunteer forces known as Awakening Councils - groups of Sunni Arab fighters who have turned against al-Qaida and are now funded by the US - have been credited with helping reduce violence in Iraq in recent months. Although bombings and other attacks continue throughout the country, their number has fallen. The US military has said there has been a 60 percent decrease in violence since June.