More than 5,000 people have fled Nigeria's northeast into neighbouring Cameroon after Boko Haram militants seized the border town of Kirawa in Borno state, residents and community leaders said on Friday.

Insurgents in Nigeria's Borno state, the epicentre of a 16-year conflict driven by Boko Haram and its splinter group Islamic State West Africa Province (ISWAP), have upped their attacks this year against civilians and security forces.

Since the start of the year, insurgents have overrun some army bases and communities in Borno, only to be beaten back by the military after seeking reinforcements.

The assault late Thursday forced the district head, Abdulrahman Abubakar, to abandon his palace, which was burned along with a military barracks and dozens of homes.

"I was left with no option but to flee to Cameroon," Abubakar told Reuters by phone. "Residents boarded trucks to seek refuge across the border, while others ran to Maiduguri," the state capital.

Boko Haram claimed responsibility for the attack, releasing a video showing fighters torching the barracks while chanting "victory belongs to God" as flames lit the night sky.

Residents said Kirawa was now deserted. "Boko Haram is in control," said Dauda Hassan, who escaped to Pulka, a neighbouring town where troops are stationed.

Thursday's attack followed a September 19 assault on Banki, another border town, where Boko Haram fighters overran a military barracks, forcing soldiers to flee and seizing weapons.

Yakubu Mabba Ali Kirawa, head of the town's development group, called for urgent military reinforcements. He told Reuters that local vigilantes and residents remain the only security presence after a multinational military task force withdrew following an attack in August.