Over 40 people were killed and 56 wounded in an army crackdown on violent anti-United Nations demonstrations in eastern Congolese city of Goma on Wednesday, the government said.

Congolese troops forcibly dispersed the protest against the United Nations peacekeeping mission and other foreign organisations after footage of an attack on a policeman circulated on social media. Reuters was unable to verify the footage.

Earlier, authorities said the policeman was stoned to death, and that six protesters were killed when the army intervened.

But in a statement on Thursday, the government said the death toll stood at 43, while 158 people were arrested. It said a military investigation had been opened.

Unverified footage posted on social media showed soldiers piling bodies into a lorry and driving them through Goma in a convoy.

The head of the local branch of the International Red Cross in Goma, Anne-Sylvie Linder, said her clinic had received a high number of people with serious stab and gunshot wounds after the protest.

"Some were dead when they arrived," she said.

The UN's peacekeeping mission in eastern Congo, known as MONUSCO, expressed its condolences in a statement and said it remained concerned by the threats of violence.

It also said it "encourages the Congolese authorities to conduct a prompt and independent investigation and calls them to treat those detained humanely and to respect their rights."

The mission has faced protests since 2022 spurred partly by complaints that it has failed to protect civilians against decades of militia violence.

An anti-MONUSCO protest in July 2022 resulted in more than 15 deaths, including three peacekeepers in Goma and the city of Butembo.