"It is a disaster...Dozens of houses were destroyed, crops have been washed away," said Jacques Minani, governor of the Bujumbura district, some 35 kilometres south of the capital.
He said rescue teams are "searching the area to try to find the missing" after the landslides overnight yesterday.
Twelve people died sheltering inside a church in the village of Rutunga, while others were killed inside their homes or simply swept away by rivers of mud, Minani added.
Mud and rocks loosened by heavy rains were swept down steep hillsides of the rural region of the small central African nation, destroying houses in its path, he said.