The UN peacekeeping mission in DR Congo said it was launching a probe after gathering evidence that its troops may have killed a young demonstrator, as a fresh protest unfolded in the east of the country on Wednesday.
"The elements that we have indicate that it was Blue Helmets who were responsible for the death of this young man," a spokesman for the mission, MONUSCO, told AFP.
The death occurred on Tuesday in the eastern city of Beni where angry locals have been demonstrating against MONUSCO, accusing it of failing to protect them against a notorious militia.
In a statement, MONUSCO quoted mission chief Leila Zerrougui as saying the man "was reportedly killed in an exchange with Blue Helmets as he was about to throw a petrol bomb".
Separately, a student was injured and 10 other people arrested on Wednesday as Congolese police broke up a demonstration outside the university in Goma, one of two cities in the province of North Kivu where anger has boiled over.
Dozens of civilians in and around the town of Beni have been killed by a shadowy group, the Allied Democratic Forces (ADF), since DR Congo's army launched an offensive against it on October 30.
The mounting toll has led people to take to the streets, accusing the authorities and MONUSCO of inaction.
On Monday, a crowd stormed one of the two UN camps near Beni and set fire to one of its offices.
Six people have been killed in the protests since Monday.
"Our demonstration is patriotic. MONUSCO is standing on the sidelines as the massacres unfold, when its chief mission is to protect civilians," one of the demonstrators in Wednesday's protest, law student Fiston Muhindo, told AFP.
"They have to go. MONUSCO is serving no purpose," said fellow law student Junior Mastaki, adding that the Congolese authorities were "incapable" of protecting the public.
Eighty-one people in the Beni region have been killed since November 5, according to a not-for-profit organisation, the Congo Research Group (CRG).
It says the ADF -- a group of Ugandan origin that has plagued eastern Democratic Republic of Congo since the mid-1990s -- has killed more than a thousand civilians since October 2014.
MONUSCO, one of the biggest UN peacekeeping operations in the world, today comprises more than 16,500 military personnel and observers, 1,300 police and at least 4,000 civilians.
But it has struggled to make headway in a vast country beset by armed groups as well as entrenched poverty and poor governance.
Responding to criticism of inaction, it has pointed out that troops are unable to deploy in combat without the approval of the host country and in coordination with national forces.
On Monday, the Congolese armed forces told AFP that they had taken "all of (ADF's) strongholds and headquarters" in the forests around Beni.
The same day, the president's office announced the DRC and UN peacekeepers would launch "joint operations" to beef up security in Beni, and the Congolese army would establish an "advance headquarters" in the town.