Bodies lay strewn on the streets of a key north-eastern Nigerian town following an assault by militant Islamists, officials have told the BBC.
The Boko Haram group attacked Baga town on Wednesday, after over-running a military base there on Saturday, they said.
Almost the entire town had been torched and the militants were now raiding nearby areas, they added.
Boko Haram launched a military campaign in 2009 to create an Islamic state.
It has taken control of many towns and villages in north-eastern Nigeria in the last year.
The conflict has displaced at least 1.5 million people, while more than 2,000 were killed last year.
Nigerian lawmaker Maina Maaji Lawan said Boko Haram controlled 70% of Borno state, which is worst-affected by the insurgency.
Musa Alhaji Bukar, a senior government official in the area, said that fleeing residents told him that Baga, which had a population of about 10,000, was now “virtually non-existent”.