Soldiers had been shelling rebel positions in the hill around the capital
Burundi's government and last active rebel group, the National Liberation Forces (FNL), have signed a ceasefire.
In the deal signed on Monday morning, both parties agreed to stop fighting by 1530 local time (1330 GMT).
The BBC's Prime Ndikumagenge in the capital, Bujumbura, says it is a significant move and is the first step in implementing a 2006 peace agreement.
More than 100 people have been killed and some 40,000 people displaced in renewed fighting since April.
Rebel spokesman Pasteur Habimana said the signing of the peace deal meant that "war would stop forever".
Our correspondent says the 2006 deal broke down after the government rejected rebel demands for power-sharing.
An FNL delegation has been in Bujumbura for the last 10 days in talks with the government.
The army had kept up its shelling of rebel positions in the hills around the capital during the talks, but this eased over the weekend, our correspondent says.
Details of the disarmament and the process of integrating rebels into military and political life - agreed under the 2006 deal - have yet to be made public.
Ex-rebel Pierre Nkurunziza was elected president in 2005 under a deal to end years of conflict between the Tutsi army and Hutu rebels.