The incident took place on Friday night in a village located in the province of Cibitoke close to the border with the Democratic Republic of Congo (DRC), the Xinhua news agency reported.
The motives and details of the attack are not specified.
According to earlier information, 23 people have been killed.
The attack came shortly before Burundians vote May 17 in a controversial referendum that could extend the president's term.
Burundi, East African country has witnessed deadly political violence since early 2015 when President Pierre Nkurunziza continued a disputed third term.