The latest effort to end Burundi's dragging political crisis ran into trouble Friday as the opposition accused the mediator of siding with government by accepting it as "legitimate".
Former Tanzanian president Benjamin Mkapa has failed to get peace talks off the ground since he was appointed in March to mediate the crisis, which erupted when President Pierre Nkurunziza decided to run for a third term in office in April 2015.
The last attempt at talks collapsed in July when government pulled out. Mkapa arrived back in Burundi on Wednesday in a bid to convince Nkurunziza to negotiate with the opposition, which the president considers a "terrorist organisation".
At a press conference on Friday, Mkapa urged the opposition to look ahead to creating "free, fair and credible elections" in 2020 and stop focusing on the events of 2015.
"I am in no position to determine the legitimacy of the government of Burundi. Elections were held, court cases were raised ... and they all said this is a legitimate process which has come to a legitimate conclusion," he said.
"Ambassadors come here, they present credentials to President Nkurunziza. The Security Council resolutions recognise him as the president of this country, so what is this foolishness? We're wasting a lot of time talking about an event that is all over."
The main umbrella opposition movement, the National Council for the Restoration of Arusha Agreement and Rule of Law (CNARED) — which is exiled in Brussels — was furious and asked the United Nations to take over as mediator.
Mkapa "has just put an end to this process, which constitutes his resignation and an admission of failure," the group said in a statement.
Nkurunziza's third-term run and victory plunged the central African nation into turmoil, with more than 500 killed in ensuing unrest. At least 300,000 people have fled the country.
A September report by UN rights experts recounted spine-chilling cases of torture and horrific sexual violence, mass arrests and disappearances and warned that "the crime of genocide also looms large."
Burundi has a long history of violence between its Hutu and Tutsi communities, which led to a 12-year civil war that ended in 2006.
Bujumbura has reacted to the mounting criticism by cutting ties with the UN's main human rights body and pulling out of the International Criminal Court (ICC), while slamming a "foreign plot" to destabilise the country.