A Boko Haram attack on a border town in Borno State forced thousands of people to flee on Monday, in a fresh assault indicating the militants’ growing ability to strike at will.

The attack on Gamboru Ngala comes after the town was almost entirely destroyed in May in a devastating assault that also left more than 300 people killed and prompted outrage at the lack of military response.

Many local residents sought refuge across the border in the north Cameroon town of Fotokol, where troop reinforcements were being sent, a security service source told AFP.

Boko Haram, which has been blamed for more than 10,000 deaths in a five-year-old uprising, has in recent weeks sought to take over a number of towns in Borno state, shifting from hit-and-run tactics to an apparent holding strategy.

The group’s leader, Abubakar Shekau, declared in a video obtained by AFP on Sunday that the town of Gwoza, southwest of Gamboru Ngala, was now under an Islamic caliphate.

Residents said Monday’s attack began at about 5:30 am (0430 GMT), with the extremists launching coordinated strikes on the main police station and a military base known as the Harmony camp.

“The sounds (of gunfire) became more deafening as police and soldiers responded to Boko Haram,” said witness Hamisu Lawan. “Most of our people have fled into Cameroon.”

Others locked themselves in their homes, voicing fears that the militants would turn their guns on civilians once they had overrun the police station and military camp.

Residents in Fotokol, which is separated from Gamboru Ngala by a river, also reported “intense” fighting throughout the morning.

“(Cameroonian) soldiers are at the bridge,” one said.

Cameroon said on August 18 that it had closed its vast border with Nigeria to guard against the spread of Ebola, which has caused five deaths in the country’s financial capital, Lagos, in the far southwest.

But few believed that Cameroon had the resources needed to seal all the possible crossing points along the roughly 1,600-kilometre (1,000-mile) frontier.

- Territorial ambitions -

Local officials and residents in Borno say Boko Haram may be in control of a key road that connects Gamboru Ngala to the state capital Maiduguri.

Establishing which parts of the area have in fact fallen into rebels hands is difficult in the remote region, where travel is dangerous and prolonged fighting has hit mobile phone networks.

In Sunday’s video, Shekau did not develop his claims about Gwoza being part of the Islamic caliphate, despite previously voicing his support for the leader of the Islamic State (IS) militants, Abu Bakr al-Baghdadi, who proclaimed himself the “leader of Muslims everywhere” in June.

Al-Baghdadi’s Sunni Muslim fighters have taken over parts of Iraq and Syria.

Nigeria’s military dismissed Shekau’s claim as “empty”, maintaining that the country’s sovereignty remained intact.

But that assertion is in conflict with multiple reports indicating that Boko Haram controls several towns in Borno and at least one in neighbouring Yobe state.

Analysts believe that Boko Haram will attempt to hold more towns in Borno in the short to mid-term, with Nigeria’s military unable or unwilling to tackle them.

Some Nigerian troops stationed in the Borno state capital, Maiduguri, have refused to deploy to retake Gwoza because of what they say are sub-standard weapons that leave them at the mercy of the better-equipped rebels.

Defence analysts have also argued that Nigeria needs to improve its counter-insurgency strategy and adapt to guerrilla fighting rather than relying on conventional means.

Others complain of a lack of political will to properly tackle Boko Haram, which wants to establish a hardline Islamic state and whose campaign has targeted schools, churches and government installations.