KIRKUK, Iraq: Four people were shot dead overnight in Kirkuk, hours after a coordinated assault on a police headquarters in the north Iraq city left 30 people dead, officials said on Monday.

The security and medical officials said that at around midnight a gunman opened fire on four men sitting in a caravan adjacent to a neighbourhood electricity generator, killing all of them.

Districts nationwide are serviced by private generators which fill the large power gap, as most Iraqis get fewer than 10 hours of electricity per day.

Typically, the generator operator and some of his friends stay in a caravan next to the generator to ensure it operates constantly.

The shooting came after a day in which 32 people were killed across Iraq, including 30 in a suicide car bombing followed by an assault by grenade-throwing gunmen on a police headquarters in Kirkuk.

The violence comes as Iraq grapples with a political crisis pitting Prime Minister Nuri al-Maliki against his government partners amid weeks of protests calling for him to resign.

No one has claimed responsibility for the attacks but local security officials blame Al-Qaeda's front group in Iraq, which often targets security forces and officials in a bid to destabilise the country and push it back towards the sectarian bloodshed of 2005 to 2008.

Kirkuk, an ethnically mixed city 240 kilometres (150 miles) north of Baghdad, lies at the heart of a swathe of disputed territory claimed by both the central government and Iraq's autonomous northern Kurdish region.

The unresolved row is persistently cited by diplomats and officials as the biggest threat to Iraq's long-term stability.

The violence was the latest in a spike in unrest that saw 246 people killed last month, the most since September, according to an AFP tally.