The six soldiers and a captain have been charged with joint participation in murder, breach of regulations and conspiracy, according to the indictment.

The video that went viral on social networks in early July 2018 showed men in military uniform summarily executing two women, blindfolded and on their knees, along with a little girl and a baby one of the mothers was carrying on her back.

The video was initially dismissed as "fake news" by the Cameroonian authorities. But Amnesty International revealed credible evidence that Cameroon's military was responsible, and the authorities later announced that the seven soldiers depicted in the video had been arrested and would be prosecuted.

For the first time, the military tribunal in Yaounde trying the soldiers allowed them to enter their pleas, all of which were not guilty, an AFP journalist reported.

The killings took place in 2015 in Zeleved, in Cameroon's Far North region where troops have been deployed to fight Boko Haram jihadists who have crossed over from Nigeria to wage attacks in the neighbouring country.

During the investigation, the six soldiers claimed they acted on orders from the captain, their superior officer, according to a lawyer involved in the case.

The captain has contested this version of events, claiming he told the soldiers to hand over the two children and their mothers, accused of ties to Boko Haram, to the police, the same lawyer added.

The tribunal has set the next hearing in the case for November 4.