Officials said the attacks appeared to be targeting mainly police officers.

Nine people were killed in the worst attack, in the central Karrada district, which is mainly Shia. The blast, near a police checkpoint, shook buildings and damaged shops.

No group has yet said it was behind the violence. Attacks in Iraq have risen since US troops withdrew in December.

In other attacks on Thursday, six people were killed by a car bomb in al-Kadhimiya, north of Baghdad, while gunmen in the Sarafiya district of the capital also killed six at a police checkpoint.

Tolls from other attacks around Baghdad include:

two dead and five injured in an explosion in the western al-Mansour district
two killed and 10 injured in two explosions in Dorat Abo Sheer, southern Baghdad
two killed and nine wounded in an attack by gunmen using weapons with silencers, targeting a police patrol in Saidiya, southern Baghdad
seven injured, most of them policemen, in a blast in al-Madaen, south of Baghdad
five civilians injured in a bomb explosion in Taji, north of Baghdad

Last week, at least 18 people were killed in a suicide attack near the Iraqi police academy in the capital.

There are fears the death toll from Thursday's violence could rise.

At least two people were killed in explosions in Baquba, the capital of Diyala province, north of Baghdad.

There are also reports of bombings in the provinces of Salahuddin and Kirkuk.

The capital of Salahuddin province is Tikrit, the home town of former leader Saddam Hussein, who was executed in 2006.

Shia targets have come under increasing attack since the government of Shia Prime Minister Nouri al-Maliki moved against senior members of the predominantly Sunni Iraqiya political bloc.

The day after US troops withdrew, a warrant was issued for the arrest of Vice-President Tariq al-Hashemi, who is accused of financing death squads.

Mr Hashemi, who denies the charges, is currently in Iraqi Kurdistan, under the protection of the regional government.

bbc.com