Cameroon‘s government has said it will investigate a video, which according to a human rights group shows the “brutal killings” of at least a dozen unarmed people by the country’s security forces.

A government spokesman said on Friday that authorities would open a probe, but added that the government was the victim of a “campaign of denigration” before a presidential election in October.

The video, circulating on social media, shows multiple persons opening fire on a group of apparently unarmed people cowering against a wall.

A man dressed in military fatigues then approaches and fires shots at close range.

Amnesty International, a UK-based rights group, on Friday alleged that the “horrifying” video provides “credible evidence” that “Cameroon’s armed forces have committed grave crimes against civilians”.

The group said in a statement that the video had been shot in the village of Achigaya in Cameroon’s Far North region.

The rights organisation said it had verified the video with digital analysis tools and were able to confirm that the video, shot prior to May 2016, “corroborates previous accounts of extrajudicial executions which the Cameroonian authorities have denied”.

Ilaria Allegrozzi, Amnesty International’s Lake Chad researcher, called for an “immediate, thorough and impartial investigation” of the footage.

“Here is yet more credible evidence to support the allegations that Cameroon’s armed forces have committed grave crimes against civilians,” added Allegrozzi.

Cameroonian government spokesman Issa Tchiroma Bakary said they would open an investigation into the video.

But he also told Reuters news agency the video was aimed at discrediting the country’s army and President Paul Biya, who has been ruling for 36 years.

“We are in an electoral period and it’s conducive to this kind of thing,” Tchiroma said.

The 85-year-old Biya announced in July he will seek a seventh term in October’s elections.

Last month a video surfaced which appeared to show two men in military uniforms shoot dead two women with children as suspected Boko Haram fighters.

Later on Friday, Tchiroma announced in a statement that authorities had arrested seven soldiers, including a lieutenant and a sergeant, in connection with the previous video.

The statement did not say when the arrests occurred.

“The Minister of Communication reiterates the Head of State’s resolve to ensure that the atrocities that may be committed by a few misguided soldiers are systematically investigated and, if need be, appropriate actions meted out,” it said.

Government and army officials had previously dismissed that video as “fake news” meant to tarnish the government’s image, even as they promised to investigate.

Since 2014, the Cameroonian elite Rapid Intervention Brigade has been fighting Nigerian armed group Boko Haram in the country’s Far North region.

The fighters have killed hundreds of people in the region with tactics including the use of child suicide bombers to attack checkpoints, marketplaces and mosques.