More bodies were being recovered on Monday, adding to the scores of others that were wrapped in bags and piled into mass graves over the weekend, local civil society sources said.
South Kivu governor Theo Ngwabidje Kasi told Reuters on Monday the death toll now stood at 401. He did not provide further details.
"The search continues because there are a great deal of bodies under the devastation," a Red Cross worker said, asking not to be named.
"Every time we manage to demolish a house, we find bodies," he added, deploring the lack of proper equipment to carry out the work.
The villages of Bushushu and Nyamukubi in Kalehe territory, South Kivu Province, were inundated on Thursday after days of torrential rain triggered landslides and caused rivers to break their banks.
"There were seven children in the family, but I'm the only one left," said Darcein Bikanaba, a survivor at Bushushu.
"My father and my mother have also gone and all my little brothers.
"We have had no help up to now... We can't stay here, it's very dangerous."
A wall of mud that fell down the mountainside on Thursday evening covers part of the village where homes and people were swept away, some into the nearby lake.
Youngsters dig into the earth. One covers his face. Another dead body has been found.
"The search continues because there are a great deal of bodies under the devastation," a Red Cross worker said, asking not to be named.
"Every time we manage to demolish a house, we find bodies," he added, deploring the lack of proper equipment to carry out the work.
"It is the worst flood we have ever had," civil society representative Christian Zihindula Bazibuhe said, adding that bodies were still floating on Lake Kivu.
The central government in Kinshasa has not yet communicated a death toll. It has sent a delegation to Kalehe and declared Monday a day of national mourning.
The United Nations' humanitarian agency OCHA said on Sunday that at least 270 deaths had been confirmed so far with more than 300 people still unaccounted for.
Around 3,000 families have lost their homes, it added.
Warming temperatures due to climate change are increasing the intensity and frequency of Africa's rains, according to United Nations climate experts.
This can increase the destruction wrought by the floods and landslides that were already common in South Kivu. Poor urban planning and weak infrastructure also make it more vulnerable to such events.
