Agathon Rwasa returned home in May to huge crowds
The leader of Burundi's last active rebel group - the FNL (National Liberation Forces) - has said that there is a plot to assassinate him.
In a letter to the president, Agathon Rwasa said army, police and intelligence officer were planning to eliminate senior FNL members.
Mr Rwasa told the BBC's Focus on Africa programme he had proof of the plot.
President Pierre Nkurunziza and Mr Rwasa held talks this week to resolve their outstanding differences.
A peace agreement signed in 2006 broke down after the government rejected rebel demands for power-sharing.
The BBC's Prime Ndikumagenge says the assassination allegations are a setback to a ceasefire agreement signed between the two parties in May, after Mr Rwasa returned home from exile in Tanzania.
The ceasefire was seen as the first step in implementing the 2006 pact.
But Mr Rwasa told the BBC the "plot" should not affect the peace process.
"I don't mean by that letter that we have to stop the [peace] process and just discuss the security of my person," he said.
He said he has not yet discussed his security fears with the president.
There are daily reports of people being killed in various incidents and the FNL says many of those being targeted are its members, our reporter says.
Mr Rwasa said that there was an attempt on his life in May, but the police have not taken any action.
He claims that weapons and mobile phones have been distributed to death squads and that money to pay them is being collected.
Ex-rebel Pierre Nkurunziza was elected president in 2005 under a deal to end years of conflict between the Tutsi army and Hutu rebels.
About 300,000 people were killed in more than a decade of civil war.