At least nine people were killed and 39 others wounded Thursday in four car bomb attacks in Iraq's Salahudin province in north of Baghdad, a provincial police source said.

A car bomb detonated in central Balad, a city some 80 km north of Baghdad, killing five people and wounding 25 others, the source told Xinhua on condition of anonymity.

Separately, a car bomb parked near a court in the city of Baiji, some 200 km north of Baghdad, exploded during rush hours in the morning, killing three people and wounding five others, the source said.

Another car bomb ripped through the city of Dujail, some 60 km north of Baghdad, killing a civilian and wounding four people, the source said.

In addition, five people were wounded when a fourth car bomb exploded outside the office of the Patriotic Union of Kurdistan ( PUK), a major Kurdish party headed by Iraqi President Jalal Talabani, in the city of Tuz-Khurmato, some 180 km north of Baghdad, the source added.

The death toll from the four car bomb attacks could rise, the source said.

The attacks in Salahudin came as a wave of similar bomb and gunfire attacks rocked Baghdad during Thursday morning's rush hours, killing 20 and wounding 64 others.

Iraqi cities have been plagued by attacks, including suicide bombings, since the U.S. troops pulled out of the country in December 2011.