The group's increasingly violent northern-based insurgency has strained relations between Nigeria's largely Christian south and its mostly Muslim north.

Here are some facts about Boko Haram:

THE GROUP:

* Boko Haram became active in about 2003 and is concentrated mainly in the northern Nigerian states of Yobe, Kano, Bauchi, Borno and Kaduna.

* Boko Haram, which in the Hausa language of northern Nigeria means "Western education is sinful," is loosely modelled on the Taliban movement in Afghanistan.

* The group considers all who do not follow its strict ideology as infidels, whether they be Christian or Muslim. It demands the adoption of sharia, Islamic law, across Nigeria.

* Recent messages from its leaders have said it is attacking anyone who opposes it, at present mainly police, the government and Christian groups.

* Boko Haram followers have prayed in their own mosques in cities including Maiduguri, Kano and Sokoto, and wear long beards and red or black headscarves.

* The group published an ultimatum this month giving Christians three days to leave northern Nigeria. Since then, attacks in northeastern Nigeria have killed many and hundreds of Christians have fled to the south. President Goodluck Jonathan declared a state of emergency on December 31 in an effort to contain the violence.

* Jonathan said the violent sect had supporters within his own government and the insecurity the group had created was worse than during the civil war that broke out in 1967 and killed more than a million people.

SOME ATTACKS BY BOKO HARAM:

* In its first attack in January 2004, it attacked a town in Yobe State before being forced to withdraw by security forces.

* In July 2009, Boko Haram staged attacks in the northeastern city of Bauchi after the arrest of some of its members, and clashed with police and the army in the northern city of Maiduguri. About 800 people were killed in five days of fighting in the two cities. Later that month, sect leader Mohammed Yusuf was captured by Nigerian security forces and shot dead in police detention hours later.

* In early July 2010, Abubakar Shekau, a former deputy leader of the sect who was thought to have been killed by police in 2009, appeared in a video and claimed leadership of the group.

* On August 26, 2011 a suicide bomber struck the U.N. building in Abuja. At least 23 people were killed and 76 wounded. Boko Haram claimed responsibility on August 29, demanding the release of prisoners and an end to a security crackdown aimed at preventing more bombings. It was the first known suicide bombing in Nigeria, marked an escalation in the group's tactics and revealed an increase in the sophistication of explosives it uses.

* On January 20, 2012 coordinated bomb and gun attacks on security forces in the northern city of Kano killed at least 186 people people - the group's most deadly attack.


Gunshots and fresh explosions were heard early Tuesday in the northern Nigerian city of Kano, even as it recovers from a series of coordinated bomb blasts that killed at least 185 people on Friday.

Police sources could not confirm if there were new casualties.

Witness Farida Tahir told dpa that gunshots were heard at around 1 am in three parts of the city.

'We could not sleep, my children were crying all through the night,' she said.

'I peeped through the window and saw teenagers dressed in military outfits, smoking and holding heavy firearms.'

Residents of Kano are currently under a 12-hour curfew, from dusk to dawn.

The terrorist group Boko Haram, which wants sharia law to be implemented across the country, claimed responsibility for Friday's attacks.

It has not yet said whether it was behind Sunday attacks on two churches and a police checkpoint in the northern town of Tafawa Balewa in which at least ten people were killed.

At least six cars packed with explosive devices were discovered by police in Kano on Monday.

Residents fear that the spate of violence that began Friday may not yet be over.