A car bomb has killed at least 13 people in Baghdad, in one of the deadliest attacks in the Iraqi capital this year.

"At least 13 people were killed and 39 wounded in a car bomb facing a popular restaurant in the Karrada area," a police colonel said.

Karrada is packed with shops and restaurants and would have been busy on Saturday night, which marks the end of the weekend in Iraq.

Eleven people were killed and more than 40 wounded in a wave of car bomb attacks on Thursday and another nine were killed in two car bombings in Baghdad on Monday.

The Islamic State jihadist group claimed it had carried out those attacks on shi'ite districts of Baghdad to avenge attacks on displaced persons from a Sunni province.

Despite the recent attacks, they have decreased sharply in number compared to the same period last year.

A curfew in operation for years in the Iraqi capital was lifted in February.

The Iraqi government is fighting a sweeping offensive by IS, which seized control of swathes of the country last June.

The army has taken back some territory from the Islamists and in April, troops seized back control of the city of Tikrit, its biggest victory of the 11-month conflict.

But many other areas remain under IS's control.