Nigeria: Boko Haram's caliphate to the fall of Gwoza

Lagos (AFP) - A timeline of developments since Boko Haram declared a caliphate based in the northeast Nigerian town of Gwoza last year until the country's military claimed its recapture on Friday:

- Islamic caliphate -

On August 24, 2014, the leader of the extremist group, Abubakar Shekau, announces that Gwoza, which the group seized in June, is part of an Islamic caliphate.

The group has also taken control of several dozen other towns and villages in the northeastern states of Adamawa, Borno and Yobe in the past months.

Since April the group has been responsible for an upsurge in violence, with suicide and other attacks and abductions, including those of 276 young girls in Chibok, a remote corner of Borno.

- Fall of Bama -

On September 2, Boko Haram fighters take over the town of Bama in Borno state, following heavy fighting with government troops, 75 kilometres (45 miles) from the group's spiritual home, Maiduguri.

Bama's fall comes several days after that of the border town of Gamboru, which had already been targeted by Boko Haram gunmen in May, razing the town and killing at least 300 people, locals say.

- Deadly attack on Baga -

On January 3, 2015, Boko Haram attacks the town of Baga on the banks of Lake Chad, where the borders of Nigeria, Cameroon, Chad and Niger converge.

Hundreds, if not more, are feared killed in what rights group say could be the militants' worst atrocity in the six-year insurgency.

- Regional countries intervene -

The attack on Baga heightens fears of cross-border attacks and a regional conflagration, prompting neighbouring countries to deploy troops to help Nigeria cope with the bloody insurgency.

On February 3, a contingent of Chadian ground troops, backed by warplanes, crosses into Nigeria for a ground offensive on Gamboru, which they wrest from the insurgents.

- Allegiance to IS -

On March 7, Boko Haram pledges allegiance to the Islamic State group in an audio message published online.

Five days later, the IS, which has declared a caliphate in parts of Iraq and Syria that it controls, welcomes the pledge.

- New regional offensive -

On March 8, the armies of Niger and Chad launch a major ground and air offensive against Boko Haram in northeastern Nigeria. A day later they recapture the town of Damasak near the Niger border.

On March 16 the Nigerian military says it has cleared Adawama and Yobe of Boko Haram insurgents.

- Gwoza retaken -

On Friday, on the eve of the presidential election, Nigeria's military announces the recapture of Gwoza, which it describes as "the headquarters of the terrorists' self-styled caliphate".