More Chibok schoolgirls have been released three years after their abduction by Boko Haram extremists, though the exact number is not immediately known, Nigerian officials said.

Boko Haram extremists are actively planning to kidnap western foreign workers in north-east Nigeria, according to the US and UK governments.

Nigerian troops have rescued 178 people from Boko Haram in attacks that destroyed several of the Islamic extremist group’s camps in the north east, according to the army.

Boko Haram extremists have abducted about 30 people including eight Cameroonian girls and killed seven hostages in two bus hijackings in Cameroon and Nigeria, Cameroon residents and a Nigerian intelligence officer said.

Nigeria’s Islamic extremists of Boko Haram have seized more towns along Nigeria’s northeastern border with Cameroon and are adopting a new strategy of encouraging civilians to stay, witnesses said, as the militants pursue their new aim to carve out an "Islamic caliphate" under their black and white flag.