Attacks, abductions: an upsurge in violence in Nigeria

Since mid-April, Nigeria has seen an upsurge of violence claimed by, or blamed on, armed Islamist group Boko Haram, including a series of bloody attacks and the unprecedented abduction of more than 250 schoolgirls.

The Islamist insurgency has left more than 10,000 dead over the past five years.

- April 14, 2014: 276 young girls are seized from their school by Boko Haram gunmen in Chibok, a remote corner of Borno state in northeastern Nigeria. Fifty-seven of the girls manage to flee, while 219 are still captive.

Boko Haram's leader Abubakar Shekau vows in a video to sell the girls as slave brides. An international effort is launched to rescue the girls.

- 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 Islamists claim responsibility.

On May 1 a bomb attack at the same bus station kills at least 19 people, and injures 80.

Much of Boko Haram's recent violence has targeted the remote northeast, the group's historic stronghold.

- May 5: Scores of Boko Haram gunmen riding in armoured vehicles raze the remote northeast Nigeria town of Gamboru Ngala in Borno state, killing at least 300 people, according to local sources. Most of the survivors flee to neighbouring Cameroon.

- May 20: Twin car bombings in the central Nigerian city of Jos, blamed on Boko Haram, kill at least 118 people and bring entire buildings down.

The twin attack comes the day the state of emergency is extended in the northeastern states of Yobe, Adamawa and Borno.

- June 1: A bomb attack targeting fans at a football match in the northeastern town of Mubi kills more than 40 people.

- June 3: Heavily armed gunmen wearing army uniforms raid four northeastern villages in Borno state, with local leaders putting the death toll as high as 400-500.

A day later another attack kills 45 on the outskirts of Maiduguri, the capital of Borno state.

- June 24: Local officials say that at least 30 people have been killed and 68 women and young girls abducted in a series of attacks over several days in Borno state. Some 63 of the captives escape in early July.

- June 25: At least 22 are killed in a bomb attack on a crowded shopping centre in Abuja, the third attack in three months on the capital. Claimed by Boko Haram.

- June 29: More than 50 are killed when suspected Boko Haram gunmen riding on motorcycles target churches in four villages near to Chibok during Sunday mass, opening fire on worshippers and chasing them into the bush.

- July 18: A massive assault by Boko Haram on Damboa in Borno state leaves "many dead", according to a local official, displacing more than 15,000 people.

- July 23: Two blasts rock northern Kaduna city killing at least 42 people, in what appears to be a double bomb attack by Boko Haram.