The two days of attacks which saw three cities rocked by explosions and gunfire were carried out by the Boko Haram group, according to a purported spokesman, Abul Qaqa, who spoke to AFP.

"We are responsible for the attacks in Maiduguri, Damaturu and Potiskum. We carried out the attacks to avenge the killings of our brothers by the security forces in 2009," he said.

"We will continue to wage war against the Nigerian state until we abolish the secular system and establish an Islamic state".

Nineteen bodies were taken to the morgue of a hospital in Damaturu while another 20 were counted at a morgue in Maiduguri, the sources said.

"So far, we have 19 bodies at the morgue, including three soldiers, three policemen and 13 civilians, they all have gunshot wounds on them. Among the soldiers, one was brought on the first day of the attack (Thursday)," said an official at the hospital in Damaturu.

Those reported killed earlier included senior police officers and a soldier in Damaturu, and police and a civilian in Potiskum.

Police in the region said officers had battled the attackers while truckloads of soldiers were seen arriving in Damaturu on Friday before authorities gave residents 30 minutes to evacuate one neighbourhood.

A Damaturu resident said suspected members of Boko Haram took to the streets on Thursday shooting and setting off explosions at random.

Residents in Maiduguri reported six explosions which sent people fleeing.

Maiduguri has borne the brunt of the violence attributed to Boko Haram, which has claimed responsibility for scores of attacks in the north as well as the August suicide bombing of UN headquarters in the capital Abuja that killed at least 24.

A military task force has been deployed in Maiduguri in a bid to stop the sect, but it has in turn been accused of major abuses, including shooting civilians and burning their homes in the wake of bomb attacks.

Damaturu was hit by coordinated attacks in early November claimed by Boko Haram which left some 150 people dead.

Earlier this week, blasts at a house in Damaturu rented by suspected members of the sect left one dead and several wounded.

Boko Haram launched an uprising in 2009 put down by a brutal military assault which left some 800 dead as well as its mosque and headquarters in Maiduguri in ruins.

It went dormant for about a year before re-emerging in 2010 with a series of assassinations. Bomb blasts have since become frequent and have grown in sophistication.

There has been intense speculation over whether Boko Haram has formed links with outside extremist groups, including Al-Qaeda's north African branch.

The group is believed to have a number of factions with varying aims.

Nigeria is Africa's most populous nation with some 160 million people, roughly divided between a mainly Muslim north and predominately Christian south.