It was gathered that Gamboru Ngala was left unguarded when the Chadian troops moved ahead days after it was liberated from the insurgents.
According to the source, the insurgents on Thursday led attacks on three Borno villages, killing not less than 20 civilians near Cameroon border.
The source said many Nigerians from the area had to flee into Kusihri village in Cameroon.
He said the insurgents stormed Gamboru Ngala town and set many homes ablaze, shot indiscriminately and in the process killed 20 persons.
He said some of the members of the youth vigilante in the area said they heard heavy gunshots from all angles, and many had to flee into Cameroon.
One of them he said, told them on phone that he saw 15 corpses lying on the path with many residents of the area whereabout yet to be known.
He added that: ”many people fled into Cameroon and Chad territories but I can’t tell casualty figure now please. ”
In a BBC Hausa Radio news broadcast monitored in Maiduguri, it was reported that the Chadian troops said 18 people were killed and many home razed down by insurgents.
Gamboru, Ngala and Foyi towns that were attacked are all Nigerian towns near border town with Chad where the Chadian troops reclaimed from militants recently