* 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 modeled 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, or Islamic law, across Nigeria.
* 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 in January 2012 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.
* Human Rights Watch said in January that the sect had killed at least 935 people since 2009.
* 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.
* In a recent success, Nigeria arrested the purported spokesman for Boko Haram on February 1, known as 'Abu Qaqa'.
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 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.
* 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.
* An attack on St. Theresa's Catholic church in Madalla on Abuja's outskirts during a packed Christmas mass, was the deadliest of a series of Christmas attacks on Nigerian churches and other targets by the sect. At least 37 people were killed.
* On January 20, 2012 coordinated bomb and gun attacks on security forces in the northern city of Kano killed at least 186 people - the group's most deadly attack.
* On February 26 a suicide bomber drove a car packed with explosives into a church in Jos, killing two people. Reprisals soon followed and Christian youths killed at least 10 people in Jos days later.