At least 65 people were killed in a spate of coordinated gun and bomb attacks in the northeast Nigerian city of Damaturu on Friday, in an attack claimed by radical Islamist sect Boko Haram.
Witnesses said dozens of bodies were piling up in morgues in the now almost deserted city.
In an interview with Nigeria's Daily Trust newspaper, a Boko Haram spokesman claimed responsibility for the attacks, and for a spate of bombings on the same day in its heartland of Maiduguri, and warned there was more to come.
Here are some facts about 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 spoken in 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 are Christian or Muslim. It demands the adoption of sharia, Islamic law, in all of Nigeria.
* Boko Haram followers have prayed in separate mosques in cities including Maiduguri, Kano and Sokoto, and wear long beards and red or black headscarves.
* 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. Some 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. He said he was ready to launch attacks on western influences in Nigeria.
* In December 2010 the group said it was behind bombings in central Nigeria and attacks on churches in the northeast that led to the deaths of at least 86 people.
* On June 16, 2011, police said they believed a suicide bomber detonated explosives that tore through a car park outside Nigeria's police headquarters in Abuja.
* The next day Boko Haram claimed responsibility for the blast, which officials said may have been the first suicide bombing in Africa's most populous country.
* On June 26 about 25 people were killed when several bombs exploded in the Dala ward of Maiduguri after suspected Boko Haram members threw bombs at a bar-cafe.
* Rights groups say more than 250 people have been killed by Boko Haram since July 2010.
* On August 25 Boko Haram members attacked Gombi police station in the northeast, killing four policemen and one soldier before driving to the First Bank and Union Bank where they killed seven staff and carried off an unspecified amount of money.
* On August 26 a car bomb struck the U.N building in Abuja. At least 23 were killed and 76 wounded by the bombing which gutted the ground floor and smashed almost all the windows. They claimed responsibility on August 29, demanding the release of prisoners and an end to the security crackdown to prevent more bombings.
Sources: Reuters/Janes World Insurgency and Terrorism, 2011
(Reporting by David Cutler, London Editorial Reference Unit)