Boko Haram extremists have killed more than 100 people and hoisted their black and white flag over a north-eastern town left undefended by Nigeria's military, according to a civil defence spokesman and a human rights advocate.
Hundreds of people in another north-eastern area, Askira Uba, are fleeing after receiving letters from the Boko Haram threatening to attack and take over their villages, Abbas Gava, a spokesman for the Nigerian Vigilante Group said.
"Nine major villages are on the run," he said.
Survivors said on Saturday that the insurgents had attacked the town of Damboa before dawn on Friday, firing rocket-propelled grenades, throwing homemade bombs into homes and gunning down people as they tried to escape the ensuing fires. Most of the town had burned down, they said.
A human rights advocate said Boko Haram had struck again as people were trying to bury their dead, and that the toll was probably much higher than 100. He spoke on condition of anonymity because he is not authorised to speak to reporters.
The only defence came from vigilantes armed with clubs and homemade rifles, Gava said.
The town had been under siege for two weeks, since Boko Haram dislodged soldiers from a new tank battalion camp on its outskirts.