The US State Department has said it is "deeply concerned" by the emergence of video footage that appears to show elements of the armed forces of the Democratic Republic of Congo (DRC) "summarily executing civilians, including women and children."

The seven-minute footage, which was provided to AFP news agency and circulated on social media by Congolese human rights activists last week, appears to show men dressed in army uniform opening fire on a group of unarmed civilians, killing at least eight of them, including women and children.

The group of eight soldiers are heard saying, "Look, they are dying" and "Watch how they get killed like animals", speaking in Lingala, the language of central Congo, and Swahili.

Reuters news agency reported the civilians may have been members of the Kamwina Nsapu militia who were singing "Our land, our land" in Tshiluba, a language of Kasai-Central.

In a statement published on 19 February, the US State Department said: "Such extrajudicial killing, if confirmed, would constitute gross violations of human rights and threatens to incite widespread violence and instability in an already fragile country."

"We call upon the Government of the DRC to launch an immediate and thorough investigation, in collaboration with international organisations responsible for monitoring human rights, to identify those who perpetrated such heinous abuses, and to hold accountable any individual proven to have been involved."

The video below, which appears to have been filed on a mobile phone on 11 or 12 February 2017, contains graphic content.

Western diplomats, United Nations officials and Human Rights Watch (HRW) representatives said the video could be used as evidence of war crimes committed by the FARDC army, which has in the past been accused of serious crimes. The video has not been independently verified.

HRW's executive director Kenneth Roth said his organisation opened an investigation over the video that seems to show Congolese soldiers "summarily massacring group of people who had been chanting."

Government spokesman, Lambert Mende, meanwhile, dismissed claims the massacre was sponsored by the government and alleged the footage was a "ridiculous montage" put together by members of the Congolese opposition.

"What kind of army would let someone film while they kill?" Mende said. "This is the work of desperate people. It's clumsy and ridiculous. It's worthy of scenes from a Rambo movie," he said.

The government later released a statement referring to possible "excesses and abuse" by soldiers after clashes in the village of Mwanza Lomba, which the video appears to show, between FARDC soldiers and Kamwina Nsapu as well as "other armed assailants".

The government statement added: "Any excesses and abuse signalled (ascribed to) elements of the FARDC in this operation" had been "taken into account in accordance with the military penal code at the end of this operation last year.

Over the last two decades the African nation has been confronted with an egregious level of impunity, amid a series of major political upheavals and ethnic and regional outbreaks of violence.

Eastern regions of the DRC are still marred by widespread violence committed by various militant groups, causing massive human rights violations, many of which qualify as international crimes.