The father of one of the Nigerian schoolgirls abducted in the northern town of Chibok has told the BBC that he has spoken to his daughter, amid reports that an unknown number of the girls had escaped from their abductors.

The man said his daughter confirmed she had fled together with other captives during fighting.

Those who managed to escape are believed to be in Maiduguri, the capital of Borno State, although there are still few details known about how they fled.

In 2014 Boko Haram militants kidnapped 276 schoolgirls from the town, sparking an international outcry and leading to personalities like Michelle Obama, then the US first lady, to campaign for their release.

Almost seven years since they were first abducted, the Chibok girls remain a powerful symbol of the security challenges plaguing Nigeria’s north-east.

Over the past six years, the authorities have managed to secure the release of more than 100 of the girls but many are still missing.

The military may try to take credit for the escape of the girls, particularly because it comes as President Muhammadu Buhari has replaced all top officials.

But last time there was a shake-up in the upper echelons of the military command, the Nigerian authorities declared Boko Haram technically defeated.

Instead the militant group has splintered in two, with both factions still carrying out regular attacks in the region.