Lagos: The Nigerian Islamist group Boko Haram, which has proclaimed a "caliphate" in the areas under its control in the northeast of the country, is now threatening neighbouring Niger, Chad and Cameroon.
The insurgency has left more than 13,000 dead and 1.5 million displaced since 2009.
Here is a timeline showing the main events since an upsurge in violence in April 2014:
- April 14, 2014: 276 young girls are seized from their school by Boko Haram gunmen in Chibok, a remote corner of Borno state in northeast Nigeria. Fifty-seven of the girls manage to flee, while 219 are still being held.
- April 14: At least 75 people die in a bomb blast in a packed bus station on the outskirts of Nigeria`s capital Abuja -- the deadliest attack yet to strike the city. Boko Haram later claims responsibility.
- May 5: Boko Haram gunmen raze the town of Gamboru Ngala in Borno state, killing at least 300 people, according to local sources.
- May 20: Twin car bombings in the central Nigerian city of Jos, blamed on Boko Haram, kill at least 118 and bring entire buildings down.
- June 3: Heavily armed gunmen raid four northeastern villages in Borno state, with local leaders putting the death toll as high as 400-500.
- October 18: Around 60 women and young girls are abducted around Chibok, according to witnesses. On October 25-26, 30 adolescents are kidnapped in the village of Mafa in Borno state.
- November 10: A suicide attack kills at least 58 people at a boys school in Potiskum in Yobe state.
- November 28: Two suicide bombers blow themselves up and gunmen open fire during weekly prayers at the mosque of the Emir of Kano, one of Nigeria`s top Islamic leaders. At least 120 people are killed and 270 others wounded.
- December 1: More than 150 people, including 44 police and security troops, die in a Boko Haram raid on the northeast Nigerian city of Damaturu in Yobe state.
- December 14: Boko Haram kills 32 people and kidnaps at least 185 others in an attack on the northeastern village of Gumsuri to the south of Maiduguri, capital of Borno state.
- January 3, 2015: In the beginning of a vast and bloody offensive, Boko Haram fighters attack the town of Baga. They seize a military base in a series of blistering raids near Lake Chad, leaving the Islamists controlling all three of Borno state`s borders with Niger, Chad and Cameroon.
- January 5: The jihadists` black flag is visible across the border, according to the mayor of one border town, Diffa in Niger. Boko Haram has controlled, since October, Malam Fatori and Damasak, near to Niger.
- January 10: A young girl, thought to be aged only 10, blows herself up at a crowded marketin Maiduguri killing 19 people. The following day four people are killed when two female suicide bombers blow themselves up at a crowded market in Potiskum.
- January 12: Cameroon`s army repels an attack by Boko Haram on a military base bear the northwest border after intense fighting.