The video appears to have been secretly filmed on a mobile phone, and depicts the detainees in squalid conditions, some of them shedding tears.

They are believed to have gone on hunger strike against their degrading treatment.

All 12 come from the English-speaking regions of the country that have been protesting against what they describe as their marginalisation by the majority francophone government.

One of the men in the video, Asaah Patrick Ndangoh, a former deputy mayor for the opposition SDF party, can be seen saying the government is responsible:

Since our abduction some six months ago we've been held hostage at various hidden cells in conditions only comparable to concentration death camps with the singular purpose to kill us.

At the moment we are held in a bunker at the gendarmerie [police] headquarters in Yaoundé.

If dying is the price we must pay to guarantee our freedom and re-establish the independence of our country, then it is a price worth paying."

Asaah Patrick Ndangoh

When I asked Communicatons Minister Issa Tchiroma about the allegations made in the video, he told me that he had not seen it.

Parents of some of those detained told me that they didn't know where their sons had disappeared to until they saw the video.

The charges against these individuals have not been made public. Mr Ndangoh had been accused by police a month ago of helping a radical anglophone MP to escape.

Dozens of other anglophones arrested in similar ways are now facing the death penalty for terrorism and endangering the security of the state.