The leader of Boko Haram, Abubaker Shekau, has proclaimed an Islamic caliphate in the north eastern Nigerian town of Gwoza, which was seized by the Islamic militants earlier this month.
The United Nations humanitarian office (OCHA) confirmed reports earlier this month that Gwoza was under Boko Harem control.
In a 52-minute video obtained by AFP Shekau said: “Thanks be to Allah who gave victory to our brethren in Gwoza and made it part of the Islamic caliphate, by the grace of Allah we will not leave the town. We have come to stay.”
Boko Haram is also believed to be in control of other areas of north eastern Nigeria including the southern part of Borno state as well as much of the territory of northern Borno and one town in neighboring Yobe state.
Experts have said the gains made by the Islamic group in recent weeks are unprecedented and they are close to creating an Islamic caliphate in northern Nigeria, mirroring what IS, the Islamic State, has done in Iraq and Syria.
But determining the exact area, which has fallen into the hands of the Islamists, is hard to do. Humanitarian workers are thin on the ground in the sparsely populated area, mobile phone coverage is poor and the region has been under a state of emergency since May last year.
However, some analysts have said that the Nigerian military could reverse the insurgents advance, although soldiers earlier this week refused to deploy to Gwoza without better weapons.
A government spokesman has said that 35 police officers at a training academy in Gwoza have gone missing. The academy was overrun by Boko Harem earlier this week. However, it is not clear if the officer have been kidnapped, killed or have gone into hiding.
Boko Haram, whose name can be translated as "Western education is forbidden,” is responsible for more than 10,000 deaths since 2009 in Nigeria.
More than 200 school girls were abducted by Boko Harem in April, although around 60 of them managed to escape. The exact whereabouts of the remaining girls is not accurately known.
The group says they want to enforce a harsh version of Islamic or Sharia law. Just half of Nigeria’s population is Christians and the rest are Muslim.