Lagos - Following are key dates and attacks blamed on Boko Haram since Nigeria's army launched a major offensive against the radical Islamist sect in May 2013.
- May 15: 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.
- June 4: Nigeria formally declares Boko Haram and Ansaru, its suspected offshoot, "terrorist" groups and issues a law to ban them.
- July 6: Gunmen believed to be from Boko Haram attack a secondary school in the northeastern state of Yobe, killing 42 people, many of whom are students.
- August 10-11: Suspected Islamist extremists kill 56 people in the northwest, including 44 in an attack on a mosque in Konduga.
- September 12: A military strike on a highly-fortified Boko Haram camp in the northeastern state of Borno kills 150 Islamists.
- September 17: An attack by Boko Haram Islamists disguised in military uniforms in the northeastern Benisheik area in Borno state kills at least 142.
- September 29: Boko Haram gunmen open fire on sleeping students in a college dormitory in northeastern Yobe state, killing at least 40 people.
- November 13: The United States blacklists Boko Haram and Ansaru as terror groups.
- December 2: Hundreds of heavily armed Boko Haram gunmen besiege an air force and army base in the northeastern city of Maiduguri, destroying aircraft, razing buildings and setting shops and petrol stations ablaze.
- December 16: The United Nations says attacks by Boko Haram have killed more than 1,200 people since May.
- December 20: Scores of suspected Islamist gunmen storm a military barracks in the northeastern town of Bama, spraying gunfire at the troops inside before torching the compound.
- January 26: At least 78 people are killed in two separate attacks in northeast Nigeria -- one on a busy market in Borno state and the other in neighbouring Adamawa, with suspicions falling on Boko Haram.
- February 15: An attack blamed on the sect leaves 106 dead in the mostly Christian village of Izghe in Borno.
- February 19: An attack by scores of Boko Haram Islamists in the northeast town of Bama kills 60 people and causes major damage to public buildings.
- Boko Haram leader Abubakar Shekau threatens attacks in the southern oil region in a new video.
- February 25: Suspected Boko Haram Islamists kill 43 people when they attack sleeping secondary school students in the town of Buni Yadi in Yobe state.
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