A series of bombs targeting Iraqi security forces ripped through busy areas in Baghdad on Monday, killing at least nine people, police said.

The violence began when two vehicles parked about 50 yards apart exploded in quick succession just after 7 a.m. as a police patrol passed by a bakery in a mainly Shiite area.

The road, which runs through a commercial district, is frequently used by police and army convoys in the eastern New Baghdad neighborhood, residents said.

Police and hospital officials said four people, including a policeman who died at the hospital, were killed and nine others wounded.

"I rushed out with others to see three bodies on the ground in pools of blood," said Mohammed Nasir, 55, who runs a food takeaway shop in New Baghdad. "This place has witnessed several bombings before and we fear that violence will come back after a period of quiet."

The U.S. military said the Iraqi police were hit when explosives planted on a truck detonated as they were responded to the initial car bomb. The U.S. military gave a lower casualty toll, saying one Iraqi policeman was killed and two civilians were wounded.

In western Baghdad, a roadside bomb struck a military convoy with a truck carrying weapons in the mainly Sunni area of Yarmouk, killing three Iraqi soldiers and wounding four bystanders, police said.

Two other roadside bombs apparently aimed at Iraqi army and police patrols elsewhere in the capital killed two civilians and wounded seven other people, police officials said.

The Iraqi officials all spoke on condition of anonymity because they weren't authorized to release the information.

Iraqi security forces have been frequently targeted as they increasingly take the lead in military operations. U.S. troops are assuming more of an advisory role and preparing to withdraw from Iraq by the end of 2011.