One resident of Kabulu village in Congo's South Kivu province lost his wife and seven children in the landslide, territorial administrator Thomas Bakenga said by phone on Saturday.
Another child was killed elsewhere, Bakenga said, adding that the death toll could rise as the search for other missing people continued.
A local civil society group said seven homes had been swept away and 31 damaged, putting the death toll at 10.
Poor urban planning and weak infrastructure across Congo make communities more vulnerable to extreme rainfall, which is becoming more intense and frequent in Africa due to warming temperatures, according to climate experts.
Heavy rain in southwest Congo caused a ravine to collapse onto a river in April, killing at least 12 people. Scores more died in similar circumstances last December.
MNA/