Member of  International Committee of the Red Cross loads relief aid for tsunami victims onto  cargo plane

Even as relief efforts begin to provide food and clean water to millions of victims of Sunday's devastating tsunamis, relief officials are saying much more is needed to prevent an even greater loss of life. Officials estimate at least 100,000 people have already died.

Relief agencies air-dropped food and supplies Thursday to some remote areas that were cut off by Sunday's series of destructive waves. Other relief workers were struggling to set up supply lines in the most stricken areas.

The emergency relief coordinator in Indonesia for Doctors Without Borders, Jan Weuts, said its teams of doctors and nurses have begun treating patients in mobile clinics in northern Indonesia's Aceh province, the area hardest hit by the disaster.

"Our activity, for the time being, is a drop in the ocean, but it's a start which is very important," he said.

Man talks on phone near smashed cars along Patong Beach in Thailand

However, devastated roads have slowed the delivery of aid to populations in remote parts of Indonesia, Sri Lanka and India. Officials say disease and hunger could potentially double the death toll if food and medical supplies do not arrive quickly.

Mr. Weuts says medical relief groups are watching for epidemics in communities that are without clean water and workable sanitation systems.

"What we try to do is set up a surveillance system," he explained, "so [we] try to contact all existing health systems still functioning, see what kind of diseases they are confronting."

The massive earthquake that set off the killer waves was centered off the Indonesian island of Sumatra. Indonesia now says more than 52,000 people are dead and tens of thousands more are missing, mostly in the province of Aceh on Sumatra's northern tip.

Sri Lanka reports more than 20,000 dead, and India says its death toll has surpassed 10,000. In Thailand, 2,000 bodies have been recovered, and 6,000 people are missing, many of them foreign tourists vacationing at the western coastal resorts of Phuket and Khao Lak.

Thaksin Shinawatra (File photo)

Thai Prime Minister Thaksin Shinawatra predicted that most of the missing would be found to have died. Still, he said rescue efforts would continue.

"We will keep on going because we still have a lot of corpses to be discovered," the prime minister explained, "and it will take some time because in the area like Khao Lak we face difficulty on the communications and the electricity."

Hundreds more died in Burma, Bangladesh, Malaysia and the Maldives, and the African countries of Somalia, Kenya, Tanzania and the Seychelles.

The United Nations says it is mounting the largest relief effort in its history, and to date more than $200 million in aid has been pledged by countries around the world.

George W. Bush

President Bush said the U.S. government is forming a core group with India, Australia and Japan to coordinate worldwide assistance.

"The United States will continue to stand with the affected governments as they care for the victims," the president said. " We will stand with them as they rebuild their communities."

U.S. officials say they are sending troops based in Japan to the region, and military ships including an aircraft carrier and helicopter carrier. A forward command post is being set up in Thailand.