"The clashes have left 20 Burundian troops and 70 DRC militants dead," a Burundian security source, requesting anonymity, told The Anadolu Agency.
Burundian army spokesman Gaspard Baratuza, for his part, said an official report on the number of casualties would be issued once the fighting wound down.
On Wednesday, Baratuza had told AA that around 200 attackers from the DRC "want to cross the Congolese border to exploit natural resources on the Burundian side of the Kibira region."
Baratuza went on to say that many of the area's inhabitants, fearing for their safety, had fled to Murwi under Burundian army protection.
One Murwi resident had told AA earlier that the recent attacks were "part of a well-planned war, given the number of attackers and their equipment."