Gunmen attacked five police posts and a prison across three cities this week, sparking responses from security forces, with the heaviest fighting concentrated in Kano, Nigeria's second city and the largest in the north.

No group claimed the raids, but the violence was likely to be blamed on Boko Haram Islamists, responsible for more than 1 000 deaths in Nigeria since mid-2009.

The militants launched gun and bomb attacks on Kano's Dala, Panshekara and Challawa police posts late Tuesday, state police commissioner Ibrahim Idris told AFP. The Goron Dutse prison was also targeted.

"All these attacks were repelled," he said. "A total of 17 extremists were killed by our men. We lost a police corporal."

He added that three suspects were arrested and were being interrogated, while officers recovered 14 improvised explosive devices as well as rifles, ammunition and vehicles following the clashes.

Kano was the site of Boko Haram's deadliest attack yet, when coordinated bombings and shootings left at least 185 people dead in January.

In Taraba state, gunmen launched an overnight attack on a regional police headquarters in the town of Wukari, killing three officers, state police spokesman Moses Olaoye said.

"Two civilians were also killed but it is not clear if they were among the attackers," added Olaoye.

Taraba is located near north-eastern states badly shaken by Boko Haram violence. It also neighbours Plateau state, hit by waves of ethnic violence as well as Islamist attacks.

In Damuturu, capital of the north-eastern Yobe state, four people were killed following a late Tuesday attack on a police station in the city's Sabon Fegi area, according to state police commissioner Patrick Egbuniwe.

"Two suspected members of Boko Haram were killed in the shootout at the police station," he said.

The rest of the attackers fled through a nearby college "where they shot dead two security guards and burned down a nearby classroom", he added.

The Islamist group's insurgency, concentrated in Nigeria's mainly Muslim north, has frequently targeted the security forces, though the group has attacked churches and other symbols of authority.

It has recently taken to attacking Christians worshipping on Sundays, leading to deadly reprisal violence from Christian mobs in the city of Kaduna earlier this month and sparking fears of wider unrest.

Nigeria, Africa's most populous nation and largest oil producer, is roughly divided between a mainly Muslim north and predominantly Christian south.

On Sunday, President Goodluck Jonathan said Boko Haram was seeking to incite a religious crisis by attacking churches in an attempt to destabilise the government.

Jonathan, who has come under heavy criticism in recent days over the spiralling violence, described how the group had moved from targeting local rivals to government institutions and now churches.

On Friday, he fired his national security adviser and defence minister.

There have been growing warnings that there could be more cases of residents taking the law into their own hands if something is not done to halt Boko Haram's attacks.

The group initially said it was fighting for the creation of an Islamic state, but its demands have since shifted repeatedly. It is believed to have a number of factions, including a main Islamist wing.

Many say deep poverty and frustration in the north have been main factors in creating the insurgency.