Issuing a desperate warning Prime Minister Ranil Wickremesinghe appealed to the people to vacate the low-lying areas in Colombo after heavy rains battered the island nation since last weekend, triggering landslides at many places.
"We will ensure that army will be deployed in the areas, so please take action to safeguard your lives by evacuating," Wickremesinghe said.
"At least 63 people were killed while 134 others remained missing in the southwestern region. Over 300,000 people are housed in relief camps and over 350 houses have been completely destroyed," officials said.
The national Disaster Management Centre said that around 200,000 people had been evacuated from the low-lying areas in the capital in an operation led by the military, involving boats and helicopters. The worst hit areas in Colombo were the city's northeastern suburbs along the Kalani river.
More From This Section
The water-level in the Kelani River was rising dangerously, threatening the low-lying areas north of the capital.
Several major reservoirs in the country are overspilling and the spill gates are open to full length to avoid dam breach - however, this has caused severe flooding downstream, officials said.
Heavy rains and strong winds have also lashed the Northern Province for the last three days. A record rainfall of 373.2 mm was recorded in the Kilinochchi District.
President Maithripala Sirisena has asked the international community for help in aid and relief work.
The President's appeal for help cames even as the Sri Lankan cricket team, on a tour to England, announced a donation of USD 7,000 for flood victims.
India has also rushed two Naval ships with relief material to Sri Lanka.
The government has announced that all flood relief goods will be exempted from import taxes.
The Ministry of Foreign Affairs ha also shared a list of relief items with the diplomatic missions in country requesting their support.
The National Building Research Organization's landslide warnings for 9 district still remain valid and people were evacuated to safe places in many high-risk areas.