Nigeria’s military authorities have imposed a dusk-to-dawn curfew on Maiduguri, capital of the north eastern state of Borno.

The curfew came as  Nigerian troops were locked in a battle with Boko Haram militants, 50 kilometres away.

It was not clear whether the curfew was imposed to forestall an impending attack on the city, a refuge for many escaping from the rural areas, which  Boko Haram militants have turned into a playground to be ravaged.

The Boko Haram militants  had mounted a pre-dawn assault on the town of Bama, hoping to extend their territorial conquests, but they ran into a stiff resistance by Nigerian troops.

Agency reports said scores of Boko Haram fighters stormed the town of Bama as the soldiers readied for a counter-attack on the town of Gwoza, which was seized by the Islamists and later declared part of an Islamic caliphate.

Boko Haram had seized a number of towns and villages in southern Borno and near the border with Cameroon, leading to fears that its aim is to make Maiduguri the centre of a hardline Islamic state.

Last week, the group seized the town of Gamboru Ngala on the border with Cameroon and nearby Madagali in neighbouring Adamawa state as part of its latest offensive.

The insurgents previously overran Buni Yadi in Yobe state, where they carried out at least three executions to enforce Islamic law, according to residents.

Nigerian troops patrolling in the streets of the remote northeast town of Baga, Borno State.

 “Troops have been battling Boko Haram fighters since 4 am (0300 GMT) in Bama as a result of an assault by the terrorists,” a senior security source told AFP on condition of anonymity.

“It is obviously a pre-emptive attack on troops that are deploying in Bama in preparation for a large-scale offensive to retake areas under the control of the terrorists.”

The fighting forced hundreds of residents to flee to Maiduguri, said one local man, Ibrahim Maigoro.

“Virtually everybody in the town has fled,” he added.

“They (Boko Haram) came in large numbers in trucks and vans and attacked soldiers who responded and the intense fighting forced us to leave our homes,” he added.

Boko Haram has taken over at least three major towns in Borno and at least one each in neighbouring Adamawa and Yobe states.

Exact details of the extent of its territorial claims are hard to verify independently, with phone networks destroyed by the fighting in the remote, dangerous region.

Nigeria’s military has maintained that the country’s sovereignty is intact and dismissed Boko Haram leader Abubakar Shekau’s declaration about making Gwoza a part of his caliphate as “empty” rhetoric.

But the apparent ease with which Boko Haram can mount attacks plus the testimonies of displaced residents strongly suggests that Nigeria’s military is unable to curb the insurgents’ activities.