Floods ground Sri Lanka President Mahinda Rajapaksa
Heavy monsoon rains have forced Sri Lanka's president to abandon a visit to areas affected by severe flooding which has displaced nearly 200,000 people and killed 18 others.
Mahinda Rajapaksa had to cancel his helicopter trip from Polonnaruwa in the east to the badly affected coastal city of Batticaloa 120km (75 miles) away.
The downpour is continuing after two weeks of rain in the centre and east.
The floods have inundated farmland and destroyed rice fields.
The eastern cities of Ampara and Batticaloa have been worst affected by the deluge, which has 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.
A number of big reservoirs have burst their banks, destroying paddy fields in a major rice-growing area.
People in some areas have told the BBC they have seen no sign of aid agencies or government relief, and that some people in makeshift camps have been missing out on meals.
Continue reading the main story Charles Haviland
BBC News, Colombo
"Every hour, the camp numbers are increasing" - the words of a Sri Lankan deputy minister, Mohammed Hizbullah, who comes from Batticaloa and says he will stay there until the situation eases.
He said there was an urgent need for milk and infant foods, mosquito nets, towels and sheets. Nearly 50 irrigation reservoirs have burst their banks and the sluices of five more have been opened as a precaution.
The chief local official said at least 15 villages were being supplied by motorboat via lagoons as road connections were cut off. The local authorities are trying to get cooked meals to marooned families, but nearly 200,000 other people have left their homes for the camps which have been set up in schools, mosques and other public places.
Long stretches of the coast to the north and south, peppered with lagoons, are also flooded. Rains are hampering helicopter transport and the president was unable to fly into Batticaloa as planned.
One official speaking to the BBC from the town of Kinniya said the water level has risen dramatically overnight and he was standing on an island. Far to the south, the village of Pottuvil is without clean water as its supply pipe has been breached.
Those displaced by the floods have squeezed into 800 camps that have sprung up in school premises, many of which are surrounded by water.
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.
Clean water and food supplies have been sent by official and international agencies to the worst-hit areas.
But the deputy disaster management minister Duleep Wijesekara said some places, such as Mutur, have been difficult to reach.
"I boarded a high-speed navy boat to get there [to Mutur], 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 added.
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.
The health ministry and relief organisations are trying to supply hygiene kits and raise people's awareness of health hazards.