The United Nations mission in the Democratic Republic of Congo called on Wednesday for officials to "respect" a protest planned by opposition groups in Kinshasa, which has been banned by the government.
A last attempt at negotiations between an opposition delegation and the Kinshasa governor, Andre Kimbuta, failed to break the impasse over the march which opposition leaders have vowed to hold Thursday.
The UN mission, known as MINUSCO, "calls on the Congo authorities to respect freedom of assembly and demonstrations as laid out in the Constitution," a spokeswoman, Florence Marchal, said at a press conference.
Felix Tshisekedi, the head of the opposition coalition, issued "a solemn and strident call on all Congolese to take to the streets of the DRC this Thursday, November 30, to show that we've had enough of this regime which is on its way out."
The country is facing a new flare-up of violence after President Joseph Kabila, who was supposed to step down after his final term last December, pushed back a new vote until December 2018.
Opposition forces are demanding "a transition without Kabila" from December 31.
Authorities made several arrests ahead of an opposition march earlier this month, sparking concern from the United States, Switzerland and Canada about limits on the freedom of expression.
According to a report this month by the respected National Episcopal Conference of the Congo (CENCO), police and security forces killed at least 53 anti-government protesters between April and October.