The Burundi army said on Thursday it had killed 68 rebels and lost four government soldiers in three days of fierce fighting.
A Burundi defence ministry spokesman said the rebels were killed in Kavumu and Musenyi in the province of Muramvya as they were about to enter a forest.
Violence has continued in Burundi despite a December ceasefire signed by the government and the FDD (Forces for the Defence of Democracy) rebels aimed at ending a war between Tutsi-led government forces and Hutu rebels that has raged since 1993, killing some 300,000 people.
Burundi's President Buyoya has repeatedly said the ceasefire cannot be implemented without African peacekeeping forces.
Officials say they expect such a force from South Africa, Mozambique and Ethiopia to start deploying in Burundi from next week.
One FDD rebel commander confirmed the fighting but said the government had exaggerated the death toll. "The toll put forward by the army is simply a propaganda, it's a wish but it is not true," he said.