The UN is to launch an appeal for emergency flood aid for Sri Lanka, where at least 37 people have died.
Nearly 390,000 people have been displaced and 3,744 houses have been totally destroyed.
The Disaster Management Agency says at least 21 per cent of Sri Lanka's staple rice crop has been destroyed, raising concerns over supply and higher food inflation.
The Sri Lankan government has put the initial estimate of damages from flooding across a third of the Island at $500 million.
Greater-than-normal monsoon rains since early January have pounded Sri Lanka's Northern, Eastern, Central and North Central provinces, setting off mudslides, swamping roads and bursting hundreds of dams and reservoirs.