Director General Sampath Kotuwegoda said relief efforts are ongoing, with 43,995 people relocated to state-run welfare centres after their homes were destroyed during the week-long heavy rains, News.Az reports, citing AFP.
The weather system is moving away from the island toward neighbouring India, but it has already caused widespread destruction, the DMC informed.
"Relief operations with the help of the armed forces are underway," Kotuwegoda told reporters in Colombo.
The effects of the weather system have been felt since Monday, although the cyclone made landfall on Wednesday, triggering record rainfall across the island.
The flooding situation in low-lying areas worsened on Saturday, prompting authorities to issue evacuation orders for those living along the banks of the Kelani River, which flows into the Indian Ocean from Colombo.
The Kelani burst its banks on Friday evening, forcing hundreds of people to move to temporary shelters, the DMC said.
Rains had subsided in most parts of the country, including the capital, but parts of the island's north were experiencing showers due to the residual effects of Cyclone Ditwah.
Officials said India had rushed a planeload of supplies early on Saturday for the victims.
Indian Prime Minister Narendra Modi expressed his condolences over the loss of life in Sri Lanka and said New Delhi was ready to send more aid.
"We stand ready to provide more aid and assistance as the situation evolves," Modi said on X.
The government has deployed the armed forces to bolster rescue and relief operations across the country, with military helicopters and boats used to evacuate marooned residents.
DMC officials said they expected flood levels to be worse than in 2016, when 71 people were killed nationwide.
This week's weather-related toll is the highest since June last year, when 26 people were killed following heavy rains. In December, 17 people died in flooding and landslides.
The worst flooding Sri Lanka has experienced since the turn of the century occurred in June 2003, when 254 people were killed.
