A fresh downpour loosened the earth on a hillside above a village in Vuveyi Lac area, burying the victims as they slept in their houses below, said Alain Kiwewa, Lubero's military administrator.
Repeated recent downpours have also raised the water table in the broader region, increasing the likelihood of flooding, said meteorology and hydrology engineer Theodore Lokakao Ilemba.
"It's everywhere in the Congo and in Rwanda, it worsens (the impact of) the rainfall and all pre-existing problems like water drainage and land use," he said.
Rains also triggered flooding and landslides in neighbouring Rwanda last week, killing 130 people and destroying more than 5,000 homes.
Writing by Alessandra Prentice; editing by Philippa FletcherOur Standards: The Thomson Reuters Trust Principles.