Tens of thousands of Sri Lankans remained unable to return to their homes on Wednesday as the death toll from devastating floods and mudslides climbed past 200, officials said.

Foreign Minister Ravi Karunanayake said 16 countries had rushed relief supplies and medicine to Sri Lanka to assist more than 600,000 people who were driven away from their homes following Friday's monsoon deluge.

"We also have a lot of enquiries from other countries and organisations wanting to know our immediate needs. We are moved by the spontaneous response," Karunanayake told reporters in the capital Colombo.

India and Pakistan have also deployed medical teams on the ground in some of the worst-affected areas, he said.

The Disaster Management Centre (DMC) confirmed that the death toll rose to 202 after the discovery of more landslide victims beneath tonnes of mud in Sri Lanka's hard-hit southwest.

READ MORE: Sri Lanka calls for international aid

Another 96 people were listed as still missing.

As the floods receded in most areas, hundreds of volunteers have fanned out to begin cleaning drinking wells to bring fresh water to survivors, officials said.

Rajitha Senaratne, a government spokesman, said additional medical teams were also being deployed to prevent the spread of waterborne diseases.

The United Nations has said it will provide water containers, water purification tablets and tarpaulin sheets while the World Health Organisation will support medical teams in affected areas.

The charity Save the Children said that about a tenth of those displaced were children below the age of five years, and raised concern over stagnant flood waters becoming breeding grounds for dengue spreading mosquitos.

Emergency teams rushed to distribute aid to another half a million people displaced by the island nation's worst flooding in more than a decade.

In May 2003, 250 people were killed and 10,000 homes destroyed after a similarly powerful southwest monsoon, officials said.

READ MORE: Death toll rises inSri Lanka floods, landslides

The DMC said the monsoon ended a prolonged drought that had threatened agriculture as well as hydropower generation.

Mudslides have become common during the monsoon season in Sri Lanka as land has been heavily deforested to grow export crops such as tea and rubber.

Last year, the monsoon rains caused flooding and landslides, killing more than 100 people in the country.