KINSHASA (Reuters) - Authorities in the Democratic Republic of Congo blocked an opposition demonstration in the capital on Saturday aimed at putting pressure on President Joseph Kabila to step down next month at the end of his mandate, witnesses said.

The rally was banned and heavily armed security forces and large police trucks blocked off key streets. They also prevented activists approaching the house of veteran opposition leader Etienne Tshisekedi, witnesses said.

“The sites where the meeting was to have taken place have been isolated,” police spokesman Pierre Mwanamputu said in a statement. Police shut down a similar protest on Nov. 5.

Kabila named opposition figure Samy Badibanga as prime minister on Thursday under a power-sharing deal that allows the president to stay in office until at least April 2018.

The main opposition bloc denounced the choice as a provocation but its attempts to stop the government’s agenda are struggling to gain traction.

The general secretary of Tshisekedi’s UDPS party on Saturday announced a new protest against Kabila to coincide with the official end of his term.

“The ... (main opposition bloc) invites all Congolese ... to a mass rally to kick off the countdown to the end of Kabila’s mandate on Dec. 19,” said Jean Marc Kabund, reading a statement. It did not spell out what action the bloc would take.

International powers fear the impasse could lead to violence in the giant Central African nation, where millions died in regional wars between 1996 and 2003. At least 50 people died in anti-government street protests in September.

Security forces arrested 17 people on Saturday in the southeastern city of Lubumbashi for wearing yellow shirts, intended to signify that Kabila was being given a ‘yellow card’ or caution, said Jose Maria Aranaz, head of the U.N. human rights office in Congo.