A post-election wave of attacks across Iraq, including car bombings in Baghdad and a northern city, killed at least 74 people, officials said Thursday.

The compiled death toll for Wednesday, with the number rising to 74 after late-night attacks, made it the bloodiest single day in Iraq in more than seven months.

It was the latest in a protracted surge in unrest fuelling fears that the country is slipping back into all-out conflict.

The wave of violence could further destabilise Iraq as political leaders jostle to build alliances and form a government following April 30 elections that left Prime Minister Nuri al-Maliki in the driver's seat for a third term in power.

In Baghdad's deadliest attack, a suicide bomber detonated a vehicle rigged with explosives in the mainly Shiite neighbourhood of Kadhimiyah in north Baghdad, killing at least 16 people and wounding 52, security and medical officials said, on condition of anonymity.

Three other car bombs blew up in the Amin, Sadr City and Jihad districts, costing 20 more lives.

The blasts were the latest in a trend of militants setting off vehicles rigged with explosives during the evening, when Baghdadis go out to markets, restaurants and cafes.

Previously, such attacks had typically been timed to go off during the morning rush-hour.

Four others were killed in shootings and bombings in and around the capital.

In Mosul, one of the most violent areas of the country, twin car bombs set off by suicide attackers killed 21 people, including 14 soldiers and policemen, in the west of the city.

Also in Nineveh province, of which Mosul is the capital, two other attacks left two people dead.

No group immediately claimed responsibility, but Sunni militants including those linked to the jihadist Islamic State of Iraq and the Levant often set off coordinated bombings across Baghdad and other major cities.

A spate of other attacks in Kirkuk and Salaheddin provinces, both north of Baghdad, left eight people dead while shelling in the militant-held city of Fallujah, a short drive west of Baghdad, killed three more.

The authorities blame external factors such as the civil war in neighbouring Syria, and insist that wide-ranging operations against militants out to sow instability are having an impact.

But near-daily attacks have continued and diplomats say the Shiite-led government must do more to reach out to the disaffected Sunni Arab minority to curb support for militancy.

The unrest comes as Maliki seeks to remain in his post after April 30 polls which gave his parliamentary bloc by far the highest number of seats.

But the bloc fell short of an absolute majority on its own and he will have to court the support of rivals, many of whom have refused to countenance a third term for Maliki.