At least 48 people have been killed and dozens injured in a wave of bombings and shootings across Iraq, police say.

The violence targeted predominantly Shia areas, in particular police officers and checkpoints.

In Baghdad, nine people died in two successive blasts in the central Karrada district. Outside the capital, at least two were killed in Baquba.

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

Tolls from other attacks around Baghdad include:

• six dead after a car bomb in Shia-dominated Kadhimiya, norht of Baghdad

• six killed by gunmen at a police checkpoint in the Sarafiya district of the capital

• 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

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.

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

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

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.

The BBC's Rafid Jabbouri, in Baghdad, says al-Qaeda in Iraq said it carried out previous waves of attacks in December and January.

However, he says he spoke to a senior government official, who said the upsurge in violence since the withdrawal of US troops was politically motivated. The official blamed Mr Hashemi for planning and co-ordinating the attacks.