Police and soldiers fired live ammunition on Friday to disperse demonstrators in the town of Beni in eastern Democratic Republic of Congo, an AFP correspondent said.
The demonstrators were protesting over the authorities failing to stop the Allied Democratic Forces (ADF) militia from killing seven civilians in the town on Wednesday.
Security forces moved in with gunfire and tear gas to disperse the protestors in the northern Boikene district at around 13:30.
There was no immediate report of casualties.
Several dozen youths fought back with stones and pieces of wood, trying to get to a base of the UN mission deployed in Congo, MONUSCO. They also accuse UN troops of doing nothing about ADF killers.
The army three weeks ago announced a "large-scale operation" against strongholds of the ADF rebels, who originated in northern Uganda and form one of a number of armed groups active on the Congolese side of the border.
The tense standoff in northern Beni was accompanied by a stoppage of normal activities in other parts of the town.
The mayor of Butembo, a trading crossroads town 54 kilometres (34 miles) to the east of Beni, told AFP that demonstrators had blocked roads in solidarity with people in Beni. Buses and taxis were not in circulation and markets were closed.
"Ten people have been arrested," said mayor Sylvain Kanyamanda. "Police will interrogate them separately to have them explain what they were doing on the public highway this morning."
"We can't mourn compatriots killed while breaching the peace. In a few moments, order will be restored," he added.
More than 60 civilians have been massacred in the Beni region since military action against the ADF began at the start of November.
The ADF began as an Islamist rebellion hostile to Ugandan President Yoweri Museveni. They fell back into eastern DRC in 1995 and have recruited people of different nationalities, but appear to have halted raids inside Uganda.