A dozen bombings in central Iraq and two shootings in the north killed 22 people Thursday, officials and doctors said, as the country suffers its worst violence in years.

Iraq has been hit by a year-long surge in bloodshed that has reached levels not seen since 2008, driven by widespread discontent among its Sunni Arab minority and by the civil war in neighbouring Syria.

On Thursday evening, four car bombs exploded in Baghdad, killing at least 11 people and wounding 47, officials said.

The bombings targeted a cafe, a market, a main street and an area of car dealerships.

Militants frequently attack places where crowds gather, such as cafes, markets, football fields and mosques, in an effort to maximise casualties.

The Baghdad blasts followed a car bombing near a checkpoint north of the capital that killed two people and wounded 15, and four others in areas south of Baghdad that killed two people and wounded eight.

North of the capital, a bomb exploded in a cafe in a town near Baquba, killing four people and wounding seven, while two more blasts in the city itself killed one and wounded three.

And two shootings in the northern city of Mosul killed two policemen.

The violence came after 10 bombings and three shootings in and around Baghdad killed at least 21 people Wednesday.

Baghdad is one of the most frequently-targeted cities in the country and is hit by near-daily bombings and shootings.

The government also faces a more than two-month crisis in Anbar province, west of Baghdad, where it has lost the city of Fallujah as well as shifting parts of provincial capital Ramadi to anti-government militants.

It is the first time anti-government forces have exercised such open control in major cities since the peak of the deadly violence that followed the US-led invasion of 2003.

More than 370,000 people may have been displaced by the violence in Anbar during the latest crisis, according to the United Nations.

Violence in Iraq has killed more than 1,800 people since January 1, according to AFP figures based on security and medical sources.