Amnesty International said Tuesday it has authenticated a video showing English-speaking separatists in Cameroon with the decapitated head of a policeman, and condemned a "horrific escalation of violence" in the anglophone regions.
It said its forensic experts had authenticated the clip, as well as another believed to be continuation of the first, in which a voice can heard saying that the separatists had taken the officer's rifle.
Amnesty International said it was not able to independently confirm the exact location where the videos were shot, but analysis suggests it might be in the area of Belo, in the North-West region.
Separatist unrest in Cameroon's two minority English-speaking regions -- North-West and South-West -- has left hundreds dead and displaced about 200,000 people since late 2016.
Years of resentment at perceived discrimination at the hands of Cameroon's majority French speakers have led to almost daily acts of violence and retribution, triggering an army crackdown.
"The brutal attacks against ordinary people and security forces are further proof of the horrific escalation of violence in Cameroon?s anglophone regions," Amnesty said.
Samira Daoud, the organisation's deputy regional director for West and Central Africa, said the situation in the anglophone regions was "becoming increasingly desperate with no one spared from the violence which is spiralling out of control."
The rights group said up to 400 "ordinary people" have been killed over the past year by both the security forces and the armed separatists.
It has also recorded more than 260 security incidents since the beginning of the year, "ranging from clashes between armed separatists and security forces, kidnappings of members of the general population and the killing of security forces by armed separatists."
Hundreds of families have been fleeing the regions in advance of the October 7 elections.
Daoud said Amnesty feared an upsurge in violence ahead of the vote. He appealed to the authorities to "commit to urgently, promptly, independently and effectively investigating" the violent incidents.