Two bombs exploded in separate attacks in Baghdad's mainly Shiite Amil district, said a police source. "A driver parked his car and went to a cigarette stall then he disappeared. Then his car blew up, killing passersby," said the police source, describing one of the attacks.

In the mostly Shi'ite al-Amin area of Baghdad, another car bomb killed eight people, medical sources said.

The attack by a suicide bomber on a checkpoint in Ramadi in western Anbar province killed five soldiers. "Before the explosion, the checkpoint was targeted with several mortar rounds. Then the suicide humvee bomber attacked it," said a police official.

"Some troops came to the scene. They were attacked by mortars. A confrontation took place for one hour."

There was no immediate claim of responsibility for the bombings. ISIS militants have in the past claimed responsibility for attacks in Baghdad and they have used bombings to fend off Iraqi security forces trying to retake Ramadi and other strongholds.

Western and Iraqi officials say U.S.-led air strikes are not enough to defeat the al Qaeda offshoot that holds parts of Iraq and Syria and is fighting to expand what it calls a caliphate.

President Barack Obama has approved sending up to 1,500 more troops to Iraq, roughly doubling the number of U.S. forces on the ground.

Iraq's government trying to revive alliance with Sunni tribesmen in Anbar province to fight against ISIS.