Rights group Amnesty International has authenticated a viral video showing the decapitated head of a Cameroonian security officer apparently filmed by separatists.

It says the footage and "brutal attacks against ordinary people and security forces" are proof of the "horrific escalation of violence" in Cameroon’s English-speaking regions.

Hundreds have been killed and more than 200,000 people forced from their homes since late 2016.

This video is the latest in a series of clips from Cameroon's violent conflict to circulate online. The Amnesty forensic experts who examined it say the gendarme had bruises on his head, which was laid on a blood-soaked cloth close to could be his genitalia. An individual identifies himself in the clip as being a member of the armed separatists group "Ambazonia Liberation Forces".

Amnesty believes the video was filmed in Cameroon's North-West region, but says it has not been able to determine the exact location.

Aid agencies' efforts to assist civilians have been frustrated by the struggle to access conflict areas. Journalists have also been denied access to conflict zones.

Presidential elections are due to take place next month, in which President Paul Biya is seeking a seventh term in office.