BAUCHI( NIGERIA): Boko Haram extremists have burned down six northeast Nigerian villages and killed 37 people near the insurgents' Sambisa Forest stronghold, a survivor said on Friday.

Ahmed Ajimi, a fighter in the anti-Boko Haram Nigerian Vigilante Group, said many victims of Wednesday night's attacks were farmers who had recently returned home after soldiers earlier this year forced the extremists out of the area where they had declared an Islamic caliphate.

Now they are refugees again, with many survivors suffering gunshot wounds and burns, Ajimi told The Associated Press in a telephone call from Biu town, 100 kilometers (60 miles) west of the destroyed villages.

Hit-and-run attacks and suicide bombings have continued. Boko Haram last week denied Nigerian military reports that militant fighters are hemmed into the Sambisa Forest and claimed its fighters still hold towns hundreds of kilometers (miles) away. There was no way to verify the competing claims.

"It was really horrifying," Ajimi said, describing the insurgents shooting from the back of pickup trucks and hurling firebombs that quickly set ablaze the thatched roofs of scores of huts.

He said he spent the night in the bush and returned yesterday to help bury 37 corpses.

The Islamic uprising is estimated to have killed some 10,000 people just last year when it began attacking neighboring countries. A multinational force this year drove Boko Haram fighters out of towns and villages they had held for months.

A summit of Nigeria and its neighbors yesterday in Abuja, the Nigerian capital, pledged to increase the force to 8,500 troops by the end of July with Nigeria pledging $30 million for the installation and equipping of its headquarters in N'Djamena, Chad's capital.

The leaders agreed to Nigerian President Muhammadu Buhari's suggestion that a Nigerian general would command the force with his deputy from Cameroon and the chief of staff from Chad.