Islamist Boko Haram militants seized a military base used by a multinational force in Nigeria's northeastern Borno state, officials and witnesses say.

The town of Baga is the unofficial headquarters of the multinational troops drawn from Niger, Nigeria, Chad and Cameroon.

The BBC quotes a senator from Borno who fled the area by boat as saying extremists moved in on Saturday as troops from the multinational force fled. A resident of Baga is quoted by the news agency as saying many people were killed and the town set on fire during the attack.

The Nigerian military did not comment on the reports.

As we reported in November, the Nigerian army claimed to had retaken another city in Borno, Chibok, home to more than 200 schoolgirls who were kidnappedand later, reportedly sold or married off by the hard-line militant group.

By way of background, Reuters says:

"The insurgency has killed over 10,000 people this year, according to a count by the Council on Foreign Relations in November. It is the gravest threat to Nigeria, Africa's biggest economy, and a headache for President Goodluck Jonathan ahead of an election on Feb. 14 where he is being challenged by opposition leader Muhammadu Buhari, a former military ruler seen as tough on security."After beginning their fight for an Islamic state five years ago in the northeastern city of Maiduguri, the militants have radiated outwards into porous border areas, threatening Nigeria's neighbours around the Lake Chad Basin."Copyright 2016 NPR. To see more, visit