At least 40 people have been killed and 21 are missing in Sri Lanka after floods and landslides triggered by heavy rains wreaked havoc this week, in one of its worst weather related disasters the country has seen in recent years.

Twenty-one people were killed in the central tea-growing district of Badulla when a landslide crashed onto their homes overnight, the Disaster Management Centre (DMC) said in a statement.

Videos uploaded to social media show houses being washed away as flood waters cascade through towns. Temporary shelters have been set up for affected families.

The country is now bracing itself for more severe weather on Friday as Cyclone Ditwah moves along its eastern coast.

Ditwah began as a deep depression off its eastern coast but later intensified into a cyclone. It is expected to make landfall in India.

In Sri Lanka, river levels are continuing to rise across and the DMC has warned residents in low-lying areas to move to higher ground. A red level flood warning has been issued for the low-lying areas of the Kelani River valley within the next 48 hours, the Irrigation Department said. Areas at risk include the capital, Colombo.

More than 200 mm of rain is expected in some central and northern parts of the island on Friday, Sri Lanka’s met office said.

Key roads connecting provinces have been closed, while train services have been heavily affected in some areas.

Students sitting for the Advanced Level Exams – also known as the A-levels – have also have their exams postponed as a result.

Sri Lanka is currently experiencing its monsoon season but it is rare for the island to see extreme weather on this level.

The worst flooding this century in Sri Lanka was in June 2003 when 254 people were killed and hundreds of thousands were displaced.