Washington - The United States and France called on the Democratic Republic of Congo to investigate a video purporting to show soldiers massacring 50 to 100 unarmed civilians in the violence-wracked center of the country.The French foreign ministry on Monday urged authorities in the capital Kinshasa to "shed light as quickly as possible on these unacceptable acts and identify those responsible, who should be held to account."The United States said on Sunday it was "deeply concerned" and also urged a "thorough investigation" into the "heinous abuses" captured in the video which was seen by AFP on Friday before appearing on social media at the weekend.In the images, a group of men are seen shooting at a group of unarmed civilians, purportedly in the central Kasai region. They appear to be soldiers and are using the army's official language. Once the shooting stops, the seven-minute clip shows the men standing amongst the bodies lying on the ground. They fire at some to finish them off, starting with a woman.The Kasai region has been plagued by violence since mid-August when government forces killed a tribal chief and militia leader, Kamwina Nsapu, who had rebelled against the central government.At least 200 people have been killed since then, leading the UN mission in the country to pledge at least 100 peacekeepers for the region.A spokesperson for the UN force, Monusco, condemned the atrocities by Nsapu's militia in early February as well as the use of disproportionate force by the national army.A DRC government spokesperson has dismissed the video as a "ridiculous fake... worthy of scenes from a Rambo movie." Two soldiers face military justice for "excesses and abuse" in Kasai, a statement said at the weekend, without specifying when the alleged crimes took place or the exact charges.As well as the tribal conflict in Kasai, DRC has been rocked by political violence after President Joseph Kabila failed to step down at the end of his second and final mandate in December.Under the terms of a power-sharing deal signed on New Year's Eve, Kabila would remain in office until the "end of 2017" but a transition council was to be established.