UN troops fired warning shots on Monday as angry protesters marched through the Central African Republic capital, Bangui, demanding that "passive" UN peacekeepers be sent home for failing to do their job.
Shops and banks in several Bangui districts remained shut as irate residents threw up roadblocks in response to an upsurge of militia violence across the country in recent weeks.
Angered by the flare-up, a coalition of civil society groups had called for a one-day strike in the city of one million to press demands for a pullout of the UN's 12,000-strong MINUSCA force.
As the protesters marched on MINUSCA headquarters at midday, peacekeepers fired warning shots into the air to hold them back, witnesses told AFP.
CAR has been in chaos since early 2013 when longtime president Francois Bozize, a Christian, was ousted by a mainly Muslim Seleka rebel group -- triggering revenge attacks and a spiral of atrocities in which thousands were slaughtered.
Fears of a sectarian bloodbath led to the dispatch of UN peacekeepers the following year.
"By staying home the population will show its support towards civil society demands for MINUSCA's withdrawal and its outrage over the killings that are taking place across almost all of the country," said the civil society coalition's coordinator Gervais Lakosso.
MINUSCA had a clear mandate to stamp out militia groups "but wherever the UN forces go there is violence," he said.
"Civil society believes MINUSCA has shown passivity and complicity."
Rejecting the allegations, UN spokesman Vladimir Monteiro said "you can't lie to Central Africans and say there are (national) armed forces that can defend them."
It would also be misleading to "just focus on the problems and forget the action undertaken," he added on Radio Ndeke Luka.
Dozens of people have been killed in recent weeks however, prompting severe criticism of the peacekeepers.
The violence between Christian and Muslim groups has displaced one in 10 of the country's 4.5 million people.
After two years of bloodshed, CAR had appeared to be returning to normal, holding peaceful elections early this year following a visit by the pope.