Ugandan President Yoweri Museveni urged Burundi's government and its opponents on Wednesday to put aside sectarian and political differences after weeks of violent protests and days of clashes with rebels in the north.
Burundi's political crisis, the worst since a civil war ended in 2005, was triggered by President Pierre Nkurunziza's decision to run for a third term in an election scheduled for July 21.
Opposition parties say his re-election bid is unconstitutional and are boycotting the race. The president cites a court ruling declaring he can run for five more years in office.
Last week, a rebel general said soldiers loyal to those behind a failed May coup attempt were behind clashes with the army in the north of the African country, one of the world's poorest nations with a history of ethnic conflict.
"I urge the people of Burundi to forget their past sectarian political differences and build their country on unity," Museveni, appointed by east African nations as a mediator to end the crisis, said via Twitter.
Museveni chaired the opening session of talks in Bujumbura on Monday between the government, the ruling and opposition parties, civil society, religious leaders and others.
He gave few indications of the topics for discussion in his opening public remarks. Ugandan Defense Minister Crispus Kiyonga is expected to lead ongoing discussions.
A senior official in the Amizero y'abarundi opposition coalition, Charles Nditije, said Museveni should demand that Nkurunziza stick to a two-term limit set out in the Arusha peace accords that ended the civil war and create a fair environment for a vote.
Some analysts have questioned Museveni's authority as a mediator. As president he has overseen the scrapping of term limits and Ugandan opposition politicians are often detained.
Museveni is expected to run in Uganda's 2016 presidential race.
"Museveni's own disregard for such limits makes him utterly unsuitable for appointment as a mediator," Chris McKeon, Africa analyst at Verisk Maplecroft said in a note.
African efforts to cool the Burundi crisis have stumbled, despite calls by the African Union and regional east African states for dialogue.
In Rwanda, Burundi's neighbor, parliament voted this week to support changing the constitution to allow President Paul Kagame to extend his rule beyond two terms.