Kano (Nigeria) (AFP) - Boko Haram militants on Monday launched a pre-dawn raid on Nigerian troops as they prepared for a major offensive to retake a town that the group's leader declared part of his Islamic caliphate.
Scores of Boko Haram fighters stormed the town of Bama as soldiers readied for an attack on the nearby town of Gwoza, which was seized by the Islamists on August 7.
Bama is just 70 kilometres (45 miles) by road from the Borno state capital, Maiduguri. The city is the radicals' spiritual home but they were chased out by the military when a state of emergency was declared in May last year.
Boko Haram has seized a number of towns and villages in southern Borno and near the border with Cameroon in recent weeks, leading to claims that it is planning to encircle Maiduguri and make it the centre of a hardline Islamic state.
A senior security source told AFP on condition of anonymity that the attack in Bama began at 4 am (0300 GMT).
The strike was "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", he added.
The security source said the insurgents suffered heavy casualties and were forced to withdraw, without elaborating.
On Twitter, the military said at @DefenceInfoNG: "#Bama attack is being repelled. We cannot state casualty situation/figures now. Everything necessary will be done to contain the Terrorists."
The fighting forced hundreds of residents to flee, adding to increasing numbers of displaced people forced out of their homes across Nigeria's far northeast because of the violence.
"Virtually everybody in the town has fled," said Ibrahim Maigoro, who fled Bama to Maiduguri.
"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."
- Territorial ambitions -
Boko Haram, which has been blamed for thousands of deaths in its five-year insurgency, has taken over at least three major towns in Borno and at least one each in neighbouring Adamawa and Yobe states in recent weeks.
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 that Gwoza was being incorporated into his caliphate as "empty" rhetoric.
But the apparent ease with which Boko Haram can mount attacks, and the testimonies of displaced residents strongly suggests that Nigeria's military is increasingly unable to curb the insurgents' activities.
Last week the group seized the town of Gamboru Ngala on the border with Cameroon and nearby Madagali in the north of the 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 soldiers have complained that they lack the weapons to fight the better-armed insurgents, who have used high-powered rocket-propelled grenades and even armoured personnel carriers in their deadly assaults.
Some troops stationed in Maiduguri last month refused to deploy to Gwoza in an apparent mutiny that was denied by the military high command.
Nigeria's government maintained in a statement on Monday that it "has the will, the resources and the strategies" to defeat Boko Haram but it added: "It will take time."
The foreign ministry meanwhile announced a one-day meeting on the Boko Haram threat in Abuja on Wednesday. Foreign ministers from Benin, Cameroon, Chad and Niger have been invited along with international representatives.