The government has confirmed 611 deaths, with another 213 unaccounted for and feared dead, in what President Anura Kumara Dissanayake has called the country's most challenging natural disaster.

The Disaster Management Centre (DMC) issued fresh landslide warnings in several areas of the worst-affected Central Province, with the northeast monsoon gathering over the island and bringing more rain.

More than two million people -- nearly 10 percent of the population -- have been affected by last week's floods and landslides, the worst this century.

Survivors will be offered up to 10 million rupees ($33,000) to buy land in a safer location and build a new house, the finance ministry said in a statement late on Friday.

They will also receive livelihood support, including cash to pay for children's school books, kitchen appliances, bedding and rent if they are not given accommodation by the state.

The government did not say how much the bold package would cost, a concern given the country's recent economic turbulence.

A senior official earlier said recovery and reconstruction might cost up to $7 billion.

The central bank has ordered commercial banks, both state-owned and private, to reschedule loans of affected people and not to impose penalties on defaulting borrowers.

The government is also offering one million rupees in compensation for each person killed or left permanently disabled.

The DMC said nearly 75,000 homes were damaged, including close to 5,000 that were completely destroyed by last week's disasters.

Around 150,000 people remain in state-run shelters, down from a peak of 225,000.

The air force said it was still using helicopters and fixed-wing aircraft on Saturday to supply communities cut off by landslides in the centre of the country.

- IMF request -

The International Monetary Fund (IMF) said on Friday it was considering Sri Lanka's request for an additional $200 million, on top of the $347 million tranche the country was already due to receive this month.

"The IMF remains closely engaged with the Sri Lankan authorities... and is committed to supporting the country," the Washington-based lender said.

Cyclone Ditwah devastated swathes of Sri Lanka as it was emerging from its severe 2022 economic crisis, following a four-year, $2.9 billion bailout loan agreed with the IMF in early 2023.

Dissanayake told parliament on Friday that Sri Lanka's economy had made a significant recovery, but was not strong enough to withstand the latest shock alone.

Despite assistance from the military and volunteers in flooded communities, fresh rains have hampered clean-up operations.

Residents evacuated from the landslide-prone central hills have been told not to return immediately, even if their homes were unaffected by the slips.