The leader of Boko Haram has claimed that the Nigerian armed group will rule a northeastern town as part of an "Islamic caliphate", a claim quickly rejected by the military.

"Thanks be to Allah who gave victory to our brethren in [the town of] Gwoza and made it part of the Islamic caliphate," Abubakar Shekau said in the 52-minute video revealed on Sunday.

Allah used us to captured Gwoza, Allah is going to use Islam to rule Gwoza, Nigeria and the whole world. Abubakar Shekau, leader of Boko Haram

The military rejected the claim, saying in a statement that the "sovereignty and territorial integrity of the Nigerian state is still intact".

Reacting to Shekau's video, Nigerian Defence Spokesman Chris Olukolade said: "Any group of terrorists laying claim to any portion of the country will not be allowed to get away with that expression of delusion and crime.

"Operations to secure that area from the activities of the bandits [are] still ongoing."

Earlier this month, heavily armed Boko Haram fighters stormed Gwoza, spraying the town with automatic gunfire, burning houses and overrunning the palace of its traditional ruler, the Emir of Gwoza.

Days later, the military launched strikes to push the Boko Haram fighters out of Gwoza, and the garrison town of Damboa, which Boko Haram sacked a month ago.

In the new video, members of the group can be seen carrying out attacks, with Boko Haram leader Abubakar Shekau declaring that the armed group has taken over the town.

"We did not do it on our own. Allah used us to captured Gwoza, Allah is going to use Islam to rule Gwoza, Nigeria and the whole world," the Boko Haram leader said.

"Some of these messages are preaches so that people can repent, some of the messages are advises, while in another way the message is a display of the way we use the power of Allah so you can fight him and that is it," he added.

No word of Baghdadi

In a July video, Shekau voiced support for Abu Bakr al-Baghdadi, the leader of the Islamic State armed group.

In the previous months, the Islamic State group has captured large swaths of in Syria and Iraq and in late June, Baghdad declared himself "the caliph" and "leader of Muslims everywhere".

But there was no indication from Shekau in the latest video that he was associating himself with Baghdadi, whose Sunni Muslim fighters have taken over parts of Iraq and Syria.

As such, it was not clear if Shekau was declaring himself to be a part of Baghdadi's call or if he was referring to a separate Nigerian caliphate.

The military has struggled to stamp out the highly mobile, combat-hardened fighters of Boko Haram, who want to carve an Islamic state out of religiously mixed Nigeria.

The group is seen as the main security threat to Africa's biggest economy and leading energy producer.

The violent five-year-old campaign of Boko Haram has been in the international spotlight since the group kidnapped more than 200 girls from a school in the village of Chibok in April. The girls are still missing.