Nineteen people were killed Wednesday in eastern DR Congo by a suspected group blamed for massacres that have sparked deadly protests against the United Nations' peacekeeping mission, the UN said.
Local administrator Donat Kibwana said 14 bodies had arrived at the morgue in Oicha, 30 kilometres (18 miles) from the city of Beni, adding that they were killed by machete.
A spokesman for the UN mission MONUSCO confirmed this figure, but later said the toll had "been revised upwards. Nineteen dead."
"The army is already at the site and is pursuing" the attackers, Kibwana said by phone from Oicha, while the MONUSCO spokesman said a "rapid intervention force" of peacekeepers was dispatched to the area in the morning.
The not-for-profit Congo Research Group (CRG) said the new massacre brought to 99 the number of civilians killed by armed groups in the Beni area since November 5, following the launch of an offensive by the country's army.
The "vast majority" of killings have been carried out by the Allied Democratic Forces (ADF), a notorious militia that has plagued eastern DR Congo since the 1990s, a CRG specialist said.
Fear and anger have prompted local people to take to the streets, accusing the authorities and MONUSCO of failing to protect them, in demonstrations that have led to seven deaths since Saturday.
The International Committee of the Red Cross (ICRC) said it was treating 27 people injured in "demonstrations in recent days".
MONUSCO said in the capital Kinshasa on Wednesday it was launching a probe after receiving evidence that its troops may have killed a demonstrator in Beni the previous day.
"The elements that we have indicate that it was Blue Helmets who were responsible for the death of this young man," a spokesman told AFP.
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".
On Monday, a crowd stormed one of the two UN camps near Beni and set fire to one of its offices.
Separately, a student was injured and 10 other people arrested on Wednesday as Congolese police broke up a demonstration outside the university in Goma, where anger also has boiled over.
"Our demonstration is patriotic. MONUSCO is standing on the sidelines as the massacres unfold, when its chief mission is to protect civilians," 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.
According to the CRG researchers, the ADF -- an Islamist group of Ugandan origin -- has killed more than 1,000 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, MONUSCO 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.