An Al-Qaeda group claimed a series of car bombs targeting Shiites in Baghdad last week as renewed violence killed seven people on Sunday amid a nationwide surge in bloodshed.

The latest attacks and claims came as authorities carried out wide-ranging operations targeting militants and implemented tight restrictions on vehicle movement in the capital in a bid to combat Iraq's worst violence since 2008.

In a statement posted on jihadi forums, the Islamic State of Iraq and the Levant claimed a spate of evening bombings targeting Shiite neighbourhoods of Baghdad on Tuesday, which it said were in retaliation for operations carried out by soldiers and police against Sunni parts of the country.

Sunni militants linked to the group frequently attack members of Iraq's Shiite Muslim majority, whom they regard as apostates.

The dozen car bombs on Tuesday killed 50 people and wounded more than 100 in the capital, security and medical officials said.

Several other attacks in Baghdad and elsewhere the same day killed 11 others.

The violence showed no signs of abating on Sunday, with seven killed in shootings and bombings.

North of Baghdad in the ethnically mixed town of Jalawla, a gunman opened fire on a police station inside a government compound, giving cover for a suicide bomber to blow himself up.

Two people were killed, including a policeman, and seven others were wounded, officials said.

Also north of the capital in Samarra, three anti-Al-Qaeda Sunni militiamen, known as the Sahwa, were shot dead.

From late 2006 onwards, the Sahwa began siding with the US military against their co-religionists in Al-Qaeda, a crucial factor in turning the tide of Iraq's insurgency.

But as a result, they are seen as traitors by Sunni militants and are often targeted.

Gunmen also attacked a checkpoint in northern Nineveh province, killing a policeman, while a magnetic "sticky bomb" attached to a car killed an electricity ministry official in a town south of Baghdad.

The violence was the latest in a surge of unrest that has killed more than 3,900 people this year, raising concerns that Iraq is slipping back into the all-out sectarian war that plagued it in 2006 and 2007, killing tens of thousands.

Authorities have responded with wide-ranging security operations targeting militants, and from Saturday began implementing tight restrictions on vehicle movement.

However, diplomats and analysts say that these measures do not address the root causes of the violence, namely anger in the Sunni Arab community at alleged ill treatment at the hands of the Shiite-led authorities.