The Sri Lankan military and aid agencies struggled Thursday to bring relief to a million people displaced by floods that have claimed nearly 30 lives and devastated the island's rice bowl.

Even as torrential rains eased overnight to bring some temporary respite, the number of people seeking protection in state-run shelters swelled to nearly 400,000, the state Disaster Management Centre (DMC) said.

The centre put the official death toll at 27. The floods were triggered by week-long rains across northern, central and eastern Sri Lanka that forced more than a million local residents to flee their homes.

Some 3,000 soldiers have been deployed in the worst-affected regions, along with trucks and air force helicopters, as UN convoys have struggled to bring crucial supplies in by road.

A large number of those forced out of their homes had only recently been resettled after decades of ethnic conflict between Tamil Tiger rebels and government forces.

"Many families were just returning home after years of displacement," said Reza Hossaini, country representative for the UN children's agency, Unicef.

"They were rebuilding their lives, children were returning to their community schools and now they all face this latest severe setback," Mr Hossaini said.

Seven trucks loaded with Unicef supplies, including water tanks, tarpaulins, chlorine tablets, sleeping mats and cooking gear, managed to reach the eastern districts of Ampara and Batticaloa late Thursday.

Residents of Batticaloa, a major rice-growing area, said it was the worst flooding in living memory.

"I have never seen anything like this before," said farmer H.A.D. Jinadasa. "It will take months to recover. I have lost everything, my fields and farm machinery."

S. Kokulan, a village official who had turned a local school into a welfare centre, said more than 3,000 people had come looking for help and shelter, although the school building was itself partially flooded.

"The men come for meals and then go back to look after their houses. As the waters go down, people are scared of looting," Kokulan said.

The region witnessed intense fighting during the separatist conflict which came to an end in May 2009, and was also devastated in the December 2004 tsunami.

Sections of the main road leading to Batticaloa from Colombo, a distance of 300 kilometres (187 miles), were still submerged, allowing only heavy weather vehicles with a high ground-clearance to get through.

"The water levels have begun to go down, but the number of people moving to state-run relief camps is going up," a DMC spokesman said, adding that more than 630 camps were up and running.

President Mahinda Rajapakse told reporters in Colombo that they were still estimating the extent of the damage, with the agricultural ministry suggesting that that nearly 20 percent of the country's rice farms had been flooded.

"We are not sparing any costs," the President said. "The relief operations are going ahead and I have told the officials to ensure that there are no delays in distributing aid."

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

The island's two main monsoon seasons run from May to September and December to February.