Soldiers have found one of the girls kidnapped by Boko Haram from a boarding school in the Nigerian town of Chibok, her uncle has said.

Amina Ali Nkeki is the first of the 219 so-called Chibok girls to be freed since the mass abduction that attracted attention around the world more than two years ago.

Yakubu Nkeki said his 19-year-old niece is pregnant and traumatised and was found wandering in a forest. He said she was brought to Chibok on Tuesday night for her identity to be verified and reunited with her mother. Her father died while she was held captive, he said.

Mr Nkeki said the soldiers then took the young woman away to a military camp in the town of Damboa.

Community leader Pogu Bitrus says other Chibok girls may also have been rescued by soldiers hunting down Boko Haram in the remote north-eastern Sambisa Forest on Tuesday night. He said he was working with officials to establish their identity.

Boko Haram Islamic extremists stormed and fire bombed the Government Girls Secondary School at Chibok on April 14 2014 and seized 276 girls who were preparing to take science exams. Dozens escaped within hours, but 219 remained missing.

The inability of Nigeria's government and military to rescue them led, in part, to the electoral defeat of President Goodluck Jonathan last year.

It is not known how many thousands of girls, boys and young women have been kidnapped by Boko Haram in a nearly seven-year-old insurgency that has killed some 20,000 people and spread across Nigeria's borders.

Nigeria's military has reported freeing thousands this year as they have forced the extremists from towns and into strongholds in the sprawling Sambisa Forest. Boko Haram has turned to soft targets using suicide bombers.