Boko Haram militants have killed at least 43 people in a five-hour assault on the town of Gubio in northeastern Nigeria's Borno state, witnesses said on Tuesday.

A convoy of around 50 Boko Haram members stormed Gubio in an assault that lasted for around five hours on Saturday afternoon and ended about 9.30 p.m., local resident Malam Yusuf Mohammed said. 

Mohammed estimated that more than 400 houses had been burned by the insurgents.

"They came, shooting, threatening to kill everybody. They set fire on many houses, burnt down our peoples' vehicles and motorcycles. We lost 43 people including two children," Abubakar Mondama, leader of a local vigilante group said.

Boko Haram has been driven out of nearly all the territory it captured by a series of offensives waged by Nigeria's armed forces backed by those from the neighbouring states of Chad, Niger and Cameroon in the past few months. Remaining militants have retreated into northeastern Nigeria's Sambisa forest.