A car bomb exploded at rush hour outside a U.S. base in the city of Baqouba (search), killing four Iraqis and wounding 12 others, police said.

Ambulances, Humvees and Iraqi police rushed to evacuate the injured at the Al-Faris, a former Iraqi air force base now used by the U.S. Army's 1st Infantry Division (search) 30 miles north of Baghdad.

The U.S. military confirmed an explosion, but could provide no further details.

The explosion occurred 10 yards from the base's main gate, said Iraqi police 2nd Lt. Ali Hussein. He said there were 12 injured and four dead among the Iraqis.

The bomb was the latest in a series of attacks on U.S. forces and their allies in the days leading to the handover of sovereignty in Iraq on June 30

A car bomb exploded Sunday near the gate of another a U.S.-run base north of Baghdad, killing six people and injuring 20 others -- including two American soldiers, the U.S. military said.