Flooding and mudslides have killed at least 151 people in Sri Lanka as emergency teams rushed to distribute aid to another half a million people displaced by the island's worst flooding in more than a decade.

Rescuers continued to pull out more bodies under enormous mudslides on Sunday, and Health Minister Rajitha Senaratne said 111 people were still missing.

However, Major-General Sudantha Ranasinghe, who is heading the search and rescue mission, told the AP news agency that he does not expect to find any more survivors.

"The situation is very dire," Al Jazeera's Minelle Fernandez, reporting from Matara in southern Sri Lanka, said. "The water levels are receding, but very slowly."

"The sheer scale and number of landslides as well as flooding around the country have stretched authorities," she said, adding that entire villages are still under water.

Soldiers took advantage of the lull in rains to clear access to most of the affected areas and the military has deployed helicopters, boats as well as amphibious vehicles to distribute aid.

The government has appealed for bottled water, new clothes and dry rations for those displaced.

Nearly 2,000 houses were damaged or completely destroyed.

One woman who had escaped a mudslide in Agalawatte, one of the worst affected areas in southern Sri Lanka, told Al Jazeera that her family was leaving their home: "There are risks so we can't stay. We have to go. We have no choice."

Jaliya Wedarachchi told Al Jazeera that his guesthouse in Tangalle, 200km south of Sri Lanka's capital, Colombo, had been swept away by floodwaters on Thursday.

"On my land where six wooden cabanas used to stand, now there is only a big hole," he said.

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The charity Save the Children said about a tenth of those displaced were children below the age of five years, and raised concern over stagnant flood waters becoming breeding grounds for dengue spreading mosquitos.

Senaratne said medical teams have been dispatched to the worst affected areas to prevent an outbreak of waterborne diseases, and said cholera and diarrhea had been successfully prevented in past floods.

"We have the expertise to deal with this situation," he told AFP news agency.

Sri Lanka has also sought international assistance, with India rushing a naval ship equipped with a medical team and other supplies on Saturday. A second Indian vessel was due to arrive in Colombo on Sunday, with a third expected on Monday, the government said.

The United Nations said it will give water containers, water purification tablets and tarpaulin sheets while the World Health Organisation will support medical teams in affected areas.

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.