"We have recorded more than 10 (deaths), therefore there is a huge mortality risk due to the fact that there is not much drinking water," said Damien Personnaz, a spokesman for the UN Children's Fund in Geneva.

“There is limited access to drinking water and living conditions in some 348 evacuation centers are extremely bad,” Personnaz said.

The UN Children's Fund (UNICEF) and the World Health Organization have expressed concern for the health of those crowded into relief centers.

The UN agencies said the lack of potable water, stagnant water, and existing weather conditions in the storm-affected areas pose a great risk to the health of the evacuees, especially the children.

Relief workers say water and medical supplies are in short supply in Real, Infanta and General Nakar, the three towns which bore the brunt of the storms and Typhoon “Yoyong” (international codename: Nanmadol) last week.

In the town of Infanta, a clinic has been set up in the local school to administer medical aid.

The center, staffed by volunteer Red Cross workers, doctors from Manila and civilian nurses, is still in desperate need of medicines.

One nurse who did not want to be named told Agence France-Presse the situation was very difficult.

"There is no potable water and medicine is in short supply. The children are already starting to come down with colds and we had to have two children flown out this morning for Manila to be treated," the nurse said. "The conditions are not good but we are coping."

But Health Secretary Manuel Dayrit told AFP the disaster area has so far been spared any outbreaks despite the thousands of people crowded into evacuation centers and the disruption of water supplies.

"What is a concern to us is the destruction of health facilities in the worst affected areas," he said.

He said the hospital in Infanta was left "non-operational."

Journalists who visited the area earlier in the week said it was half-submerged in mud, with medicines and intravenous bottles lying in the dirt.

Many local clinics were also damaged and local health personnel displaced by the storms and floodwaters, which still cover much of the region.

"The health situation can deteriorate anytime because of the destroyed property," said Dayrit.

A Philippine Coast Guard ship, with medical facilities, has docked in the port of Real as two US Navy Seahawk helicopters flew shuttle missions between Manila and the worst hit towns along the east coast of the main island of Luzon.

Dayrit said health workers had been sent to the ravaged towns along with supplies of medicine and drinking water to avoid any outbreaks.

But he said overcrowding in the evacuation centers was decreasing as more people were returning to their homes.