The African Union has warned that the political crisis in Burundi could have catastrophic consequences for the country and the surrounding region.
The statement, by AU Commission chief Nkosazana Dlamini-Zuma, comes a day after the killing of former military chief Jean Bikomagu.
Unidentified gunmen killed Bikomagu outside of his home in the capital, Bujumbura. The death follows the recent assassination of the president's security advisor Adolphe Nshimirimana.
"This despicable act, and multiple other acts of violence recorded in recent months, illustrates yet again the gravity of the situation in Burundi - and the real risk of seeing a further deterioration with catastrophic consequences both for the country itself, and for the whole region," Dlamini-Zuma said in the statement said.
She stressed the need for dialogue to find a peaceful and lasting solution to the current crisis.
The country has been rocked by violence since April when President Pierre Nkurunziza announced plans to run for a third term in office. His decision triggered a failed coup in June and clashed that left more than 100 people dead. Critics say Nkurunziza actions undermined the constitution and the Arusha accord, which effectively ended the country's 13-year civil war.
Burundi's constitutional court ruled he was eligible to run because he was first elected by parliament, not voters, in 2005.
The July 21 vote in which Nkurunziza was re-elected was widely viewed as flawed.