More than 140 people have been killed in a series of bombings and attacks by Islamist militants in the northern Nigerian city of Kano.

Soldiers and police officers are out in force in the city, where gunfire is still ringing out in some quarters.

The Islamist group Boko Haram, which has been blamed for hundreds of deaths in recent months, has claimed responsibility for the attacks.

A mortuary attendant at Murtala Muhammad hospital, the largest in Kano, said they had 143 bodies of people who died in the attacks, which began at 5pm on Friday afternoon after prayers.

The Associated Press reported that there were soldiers and police officers among the dead.

Nwakpa O Nwakpa, a spokesman for the Nigerian Red Cross, said officials were continuing to collect corpses scattered around sites of the attacks.

"From what they are saying, there are many involved, either wounded or dead," Nwakpa said.

A survey of two hospitals by the Red Cross said at least 50 people were injured in Friday's attack, he added.

Witnesses reported seeing at least 100 bodies sprawled around the regional police base alone.

Federal police spokesman Olusola Amore said the attackers targeted five police buildings, two immigration offices and the local headquarters of the State Security Service, Nigeria's secret police.

He appealed for people to "come forward with information on the identity and location of these hoodlums".

A massive blast caused when a suicide bomber who drove a car full of explosives into a regional police headquarters shook cars miles away. Inmates at the regional police headquarters fled amid gunfire, witnesses said.

State authorities declared a 24-hour curfew late on Friday as residents hid inside their homes amid the fighting.

A Boko Haram spokesman, using the nom de guerre Abul-Qaqa, claimed responsibility for the attacks, which he said were retaliation at the state government refusing to release members of the Islamist terrorist group.

Boko Haram, which seeks to implement strict Sharia law across Nigeria, is responsible for at least 510 killings last year, according to AP. The group has been blamed for at least 76 killings this year, the news agency added.

The targets of Boko Haram, whose name means "western education is sacrilege" in the local Hausa language, have included both Muslims and Christians. But the militants have promised to kill any Christians living in Nigeria's predominantly Muslim north.

Analysts say the sect has so far failed to gain significant traction outside its 'home' states of Yobe and Borno. But the group stages shootouts on police targets in the north on a daily basis.

The group previously claimed responsibility for Nigeria's first ever suicide car bombing in August that targeted the UN headquarters in the capital, Abuja, killing 25 people and wounding more than 100.

The sect killed at least 42 people during a series of attacks on Christmas Day, which included the bombing of a Catholic church outside Abuja.

"The temptation is going to be to see these attacks as an indication of greater co-ordination to which I would say maybe, maybe not," said John Campbell, the former US ambassador to Nigeria.

"It's not rocket science for the various groups to go around planting bombs in government headquarters."