Flooding in Sri Lanka has forced more than 1 million people out of their homes.

At least 23 people have died during a week of monsoon floods, with the centre and east of the island worst hit by rising water levels and mudslides.

A spokesman for the disaster management centre in Colombo said the eastern district of Batticaloa, which saw bloody fighting in the civil war that ended in 2009, was badly affected after heavier than usual seasonal rains.

"Some 541,000 people have been displaced in Batticaloa district alone where we have set up 275 camps to accommodate them," the spokesman said, adding that a total of 1,081,000 people have been displaced.

More than 350,000 people have taken shelter in state-run relief camps while other displaced people have moved to higher ground, often staying with friends or relatives, he said.

Retired school principal K Ratnavel, 63, said half of the coastal village of Ailadivembu, about 60 kilometres south of the Batticaloa town, was under water.

"My house is under six feet of water and I moved into a government building with my wife and three children," he said.

"We only have the clothes we are wearing. Everything else is lost.

"There are about 15,000 people at the local council office where we are sheltering and most of them need clothing."

He said many homes devastated by the December 2004 tsunami were affected by floods.

Rising water and continued rain have swamped vast tracts of land and cut off villages.

President Mahinda Rajapakse said that it was "the duty of all to join hands and help [the victims] at this hour of need without any discrimination or petty considerations".

Bad weather forced Mr Rajapakse to abandon a helicopter tour of flood-affected areas on Wednesday.

Security forces have been assisting the relief operations and 3,000 soldiers have already been deployed in the east. Air force helicopters and navy boats were also helping out.

The United Nations and local and international aid agencies are assisting relief operations.

Seven trucks loaded with UNICEF supplies, including water tanks, tarpaulins, chlorine tablets, sleeping mats and cooking gear, have been sent to Ampara and Batticaloa districts.

Sri Lanka depends on monsoon rains for irrigation and power generation, but the seasonal downpours frequently cause death and damage to property in low-lying areas as well as mountainous regions.

- AFP