Following are the main attacks linked to the Boko Haram extremist Islamist group in Nigeria.

Violence by the group, which is demanding the creation of an Islamic state in mainly Muslim northern Nigeria, has left several thousand dead in the north and centre of the country since 2009.

- November 4, 2011: A series of attacks on police targets and churches in the northeastern city of Damaturu claimed by the sect kills at least 150 people.

- January 20, 2012: At least 185 people are killed in the northern city of Kano following coordinated bombings and gun battles, claimed by Boko Haram.

- April 19, 2013: Fierce fighting between troops and suspected Islamists in the remote northeastern town of Baga kills 187 people while 77 others are injured.

- May 7, 2013: Boko Haram launches coordinated attacks in the northeastern town of Bama, killing 55 people and freeing 105 inmates.

- May 15, 2013: Nigerian troops begin an offensive against Boko Haram in the states of Borno, Yobe and Adamawa, where a state of emergency is declared in order to retake areas which have fallen into the hands of the insurgents.

- September 17, 2013: An attack by Boko Haram Islamists disguised in military uniforms in the northeastern Benisheik area in Borno state kills at least 142 people.

- February 15, 2014: An attack blamed on the sect leaves more than 100 people dead in the mostly Christian village of Izghe in Borno.

- April 14, 2014: A blast at a bus station packed with morning commuters at Nyanya, on the southern outskirts of Abuja, kills at least 72 people, in the most deadly attack to date on the capital. Most of the previous attacks have taken place in the group's historic stronghold in the northeast.