At least 21 people were killed and 82 injured Tuesday in a series of car bomb explosions in Iraq's capital Baghdad, an official source said.

The attacks occurred in the morning when seven car bombs went off almost simultaneously in eastern Baghdad, the source told Xinhua.

One of the car bombs detonated in Sadr City district in eastern Baghdad and killed a civilian and injured nine, while another car bomb went off in the same area, killing two people and injuring six, the source said.

Another bomb struck the nearby district of Jamila, leaving a civilian dead and 10 others injured, while three people were killed and 10 injured when another car bomb ripped through Baladiyat district in eastern Baghdad, the source said.

A car bomb went off at an intersection in Ur district in northeastern Baghdad, killing two people and injuring eight. Separately, a car bomb exploded at a commercial area in Karrada district in southeast of capital, injuring 12 people, the source added.

Meanwhile, a civilian was injured in a car bomb explosion in Amil district in southern Baghdad, he said.

In northern Iraq, back-to-back suicide car bombs struck an army base at a village outside Riyadh near the city of Kirkuk, leaving two people dead and 11 soldiers injured, besides destroying three military vehicles, a police source said.

In a separate incident, a booby-trapped car detonated at a parking lot outside a main hospital in the city of Balad, some 80 km north of Baghdad, killing five people and injuring 15, the police source said.

In Anbar province, an Iraqi army force clashed with gunmen and killed five militants apart from destroying two vehicles, one of them carrying a heavy machine gun, the provincial joint operations command said in a statement.