An unknown armed gang killed at least 23 people on Friday night in an attack on a village in northwest Burundi, a local official said.
"We have already counted 23 people killed, including men, women and children, but the toll could increase as we continue to search for victims," the official told AFP on condition of anonymity.
Witnesses said a further 10 people were wounded in the raid by a group armed with guns and knives who also set fire to buildings in a village in the Cibitoke province bordering the Democratic Republic of Congo and Rwanda.
"These criminals went house to house and committed real carnage," said the official.
"Some of the victims were stabbed, others were shot, there is even a whole family that was burned alive in their home."
The perpetrators and their motive are not yet known, but local residents said the attackers crossed into DR Congo after carrying out the raid at around 10 pm (2000 GMT) on Friday night.
The attack comes as tensions rise days ahead of a constitutional referendum in Burundi which could allow President Pierre Nkurunziza to stay in power until 2034.