Journalists in the Democratic Republic of Congo say they have reviewed a video that appears to document the violent deaths of United Nations experts Zaida Catalan and Michael Sharp in March.

Government officials made the video available to reporters in Kinshasa on Monday, stressing that the dress and manner of the attackers clearly identified them as Kamuina Nsapu militants. The video was evidence that Congolese security forces were not responsible for the attack, spokesman Lambert Mende said.

News outlets including Bloomberg and The Guardian said Mende did not explain how the DR Congo government acquired the video, nor were they able to independently confirm the killers’ identities.

Catalan, of Sweden, and the American Sharp went missing on March 12 in the Kasai Province. Their bodies were found in shallow graves two weeks later. The United Nations is conducting their own investigation into the incident, and has called on Congolese authorities to complete a thorough inquiry.

Violence in the Kasai regions has increased since last August, when Congolese security forces killed Jean-Pierre Mpandi, an anti-Kabila traditional leader with the title of Kamuina Nsapu. The militia groups that have taken the name, as well as government forces, both stand accused of being responsible for human rights violations and at least 400 deaths in Kasai and the surrounding provinces.

Another 225,000 people have been displaced by the fighting, according to recent UN figures, but those numbers have likely increased as thousands of Congolese in recent weeks have fled to Angola to seek refuge from the intensifying conflict.