Much of Batticaloa is under water More than 30,000 army, navy, police and air force personnel have been deployed across Sri Lanka to provide urgent aid to people hit by heavy flooding.
A government spokesman told the BBC that more than 325,000 people had been displaced by the floods, which have killed at least 21 people.
The priority since the rains abated on Thursday is to deliver emergency food and medical supplies.
In the centre and east farmland has been flooded and rice fields destroyed.
Thousands of people who fled the flooding are now living in camps on higher ground, a spokesman from the disaster management centre told the BBC.
But officials say that in some cases those camps in turn have been flooded – it is estimated that 25 out of 200 have been inundated in the coastal area of Batticaloa.
“More than one million people have been affected by the floods,” UN children’s fund spokesman Mervyn Fletcher told the BBC from Colombo.
“That means they have either been forced from their homes or have seen their property flooded.
“Access to clean water is becoming a major problem and we and other agencies are distributing purification tablets.”
Mr Fletcher said that the floods were especially bad news for people in the east, who in recent years have also endured a civil war and a tsunami.
The floods have left some stretches of railway line under nearly a metre of water.
Officials in Ampara say the rainfall there since Saturday has been the highest ever recorded in such a short time.
Over a million people have seen their homes flooded “There is a shortage of food for children,” a member of Sri Lanka’s minority Muslim community in Ampara told BBC Tamil on Wednesday.
“In the morning we were forced to divide a single breakfast food parcel into four and give it to our four children.
“We have not got any help from the government. But the local people – especially the rich – have come forward and helped us. We are only getting something to eat because of their generosity.”
A number of big reservoirs have burst their banks, destroying paddy fields in a major rice-growing area.
People in some remote areas on Wednesday told the BBC they had seen no sign of aid agencies or government relief, and that some people in makeshift camps had been missing out on meals.
In other developments:
People in the central districts of Matale and Badulla are being evacuated because of the landslide threat, authorities sayThe price of vegetables has risen sharply because there is no means of transportation to the wholesale marketsThe temperature in Colombo dropped to 18.8C on Wednesday – the lowest recorded for 61 years, the Met Department saidThe Indian government says it will dispatch relief material for the flood-affected people, with the first consignment arriving on Friday
People in Batticaloa district told the BBC Tamil service on Wednesday that they had done their best to stay in their villages, but had been forced to flee in the end.
The air force has helped evacuate people and drop food supplies to some cut-off communities.
The government has made an emergency appeal for ordinary people’s help in sending dry rations, mattresses and bottled water.
Deputy Disaster Management Minister Duleep Wijesekara said on Wednesday that some places, such as Muttur, had been difficult to reach.
“I boarded a high-speed navy boat to get there [to Muttur], but due to the huge waves we had to turn back after sailing for about 15km. After that we had to send food in by air,” he said.
The floods bring a risk of disease, including the mosquito-borne dengue fever, which even in normal times is a severe problem in the country.
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