A detachment of Nigerian troops fired into the air on Sunday - at an airport in the north-eastern city of Maiduguri - to protest against their redeployment to the frontline of the conflict against Islamist militants.

Local media reported that the soldiers refused to board the plane that was to transfer them from Maiduguri, the capital of Borno state, to the town of Marte, close to the border with Niger.

Witnesses said the soldiers were shooting for around four hours from 18:30 local time (1730 GMT), news agency Reuters reports.

“We are angry and that is why we are shooting. Why are they taking us again to another place after spending about four years?” said a soldier, adding that they had previously been told they would only fight insurgents for a maximum of three years.

The military has not officially commented on the incident.

Henrietta Yakubu, a spokeswoman for the Federal Airport Authority of Nigeria (FAAN), said she was told the protest had ended. “The situation has normalised."

She said the protest had not forced the airport to shut down.

Reuters reports that it was unable to independently verify whether the protest had ended.

BBC correspondents say there is growing discontent in the military at the nine-year campaign against Boko Haram despite the government having said since December 2015 that they had technically been defeated.