Heavy rain has lashed Sri Lanka triggering floods and landslides that have killed at least 17 people and forced tens of thousands from their homes, officials said on Monday.

After days of rain, rivers on the island nation's southern and western plains overflowed on the weekend, inundating low-lying areas and forcing thousands into relief centers.

"Water levels are receding but landslide warnings are still in place in 10 districts," Pradeep Kodippili, assistant director of the National Disaster Management Centre, said in a statement.

More than 270,000 people have been affected and about 100,000 buildings lost power, he added.

"We expect the rainfall to reduce from now on but intermittent rains will be seen in some areas," said meteorological department director general Athula Karunanayake.

The natural disaster comes as Sri Lanka is hoping to ease restrictions to tackle the novel coronavirus. A month-long lockdown to fight a third wave of infections is due to end on June 14.

Sri Lanka's tourism sector has been badly hit by the pandemic.