Sri Lanka has sought international assistance, with India sending two naval ships laden with supplies over the weekend.
Colombo: Sri Lanka's monsoon toll climbed to 164 with the discovery of more bodies of people buried in landslides triggered by intense rains, the Disaster Management Centre (DMC) said Monday.
Friday's deluge also caused the island's worst flooding in 14 years and drove nearly half a million people out of their inundated homes in the southern and western regions.
The DMC said 104 people were still listed as missing while another 88 remained in hospital.
Police said an air force Mi-17 transport helicopter crashed in the southern Baddegama area Monday while transporting relief supplies to flood victims.
"The helicopter crashed onto a house, but fortunately there were no casualties," a police official in the area told AFP by telephone.
The air force has deployed a dozen aircraft for mercy missions to evacuate marooned villagers as well as carry food and other essentials to the affected areas.
The government said relief operations had intensified over the weekend following a break in the monsoon rains.
However, the meteorological department said it expected more rain on Monday and Tuesday that could hamper relief operations.
Flood waters were receding in the worst affected districts of Ratnapura and Kalutara but the authorities said cleaning up operations could take weeks.
Nearly 2,000 houses were damaged or destroyed. Sri Lanka has sought international assistance, with India sending two naval ships laden with supplies over the weekend.
The United Nations said it would donate water containers, water purification tablets and tarpaulin sheets while the World Health Organization will support medical teams in affected areas.
Pakistan was in talks with Colombo to send relief supplies. Islamabad recently gave 10,000 tonnes of rice to Sri Lanka to help drought victims.
The meteorological department said the rains ended a prolonged drought that had threatened agriculture as well as hydropower generation.
The flooding is the worst since May 2003 when 250 people were killed and 10,000 homes destroyed after a similarly powerful monsoon, officials said.
Monsoon rains last year caused flooding and landslides, killing more than 100 people.