Car bombs struck across Baghdad on Thursday, killing at least 20 people and wounding dozens, in the latest wave of attacks on the Iraqi capital since a political crisis erupted in December, security officials said.

One car bomb killed at least nine people and wounded 27 in the upmarket Karrada neighbourhood, hurling shrapnel into the next street and blowing out glass from nearby buildings. At least two other blasts hit Karrada, including another car bomb attack that killed one person, police said.

Witnesses saw at least four wrecked cars full of shrapnel and bloodied seats near a popular, ice-cream shop in Karrada.

In the Iraqi capital's northwestern Kadhimiya district, a car bomb killed six people and wounded others when it struck a street lined with restaurants.

Another car bomb targeting a police patrol in the mixed Mansour neighbourhood killed two people, police said. Twin roadside bombs killed two people and wounded 9 in a mostly Shiite district of the southern Doura neighbourhood.

Tensions have been high in Iraq as it struggles with its worst political turmoil in a year in the aftermath of the U.S. troop withdrawal nearly nine years after the invasion that ousted Saddam Hussein.

Attacks against mostly Shiite targets surged after Shiite Prime Minister Nuri al-Maliki's government moved against senior members of the Sunni-backed Iraqiya political bloc.

On Sunday, a suicide car bombing killed 19 people at a Baghdad police academy.

While violence has ebbed since the height of the war, Al-Qaeda affliliated Sunni Islamist insurgents are still capable of major attacks. They often target government buildings and Iraqi security forces.

Maliki's fragile coalition of Sunni Arabs, Shiites and Kurds is negotiating to ease the crisis, which revived fears of a return to the sectarian strife seen in 2006-2007 when tens of thousands of Iraqis were killed.

In January a suicide bomber killed 31 people in a Shiite funeral procession in Baghdad's Zaafaraniya neighbourhood. Days earlier a suicide bomber killed 53 in an attack on Shiite pilgrims in Basra in southern Iraq.