US helicopters have begun dropping food and medical supplies in isolated parts of Aceh province in Indonesia that were worst hit by last Sunday's tsunami.
Some Acehnese victims are finally getting help after seven days
Many remote communities there have been completely cut off and it is difficult to get aid in, relief workers say.
In the second-worst affected country, Sri Lanka, there were fears of disease after heavy rains and flash flooding.
In India, supplies were air-dropped onto Andaman and Nicobar islands after criticism that aid was slow to arrive.
More than 124,000 people have been confirmed dead across Asia - three-fourths in Indonesia alone.
The United Nations says the number exceeds 150,000 and may never be known as many bodies have been washed out to sea.
But people are still being found alive seven days after the disaster. The latest was a fisherman found under his boat which was flung by the waves onto the shore in Indonesia.
In other developments:
- US Secretary of State Colin Powell and President George W Bush's brother Jeb head for Thailand and Indonesia later on Sunday to see the devastation at first-hand
- Police in Thailand say thousands of local people are still missing, presumed dead, in the town of Baan Nam Khem in Phang Nga province
- The UN puts the overall number of people in need of food aid at 1.8m and urges more protection for thousands of orphans
- The leader of the worldwide Anglican Church, the Archbishop of Canterbury, Rowan Williams, says the devastation in Asia will make believers in God question their faith.
Unable to land
About 12 American Seahawk helicopters are now delivering aid from a US aircraft carrier stationed off the coast of western Aceh, near the epicentre of the earthquake.
The area has been completely cut off for a week, the BBC's Rachel Harvey reports from the provincial capital, Banda Aceh.
A vast swathe of coastline which was home to tens of thousands of people has been wiped out and survivors are living in a sea of mud without shelter or clean water.
Aid deliveries are relying on helicopters as the only way to reach the most remote areas but they are often unable to touch down because of mobs of people on the ground running towards them desperate for help.
"They were pushing to get into the cabin to get to the food," Petty Officer Brennan Zwak of the US Navy told BBC News.
The authorities in and around Banda Aceh say they are burying 3,500 to 4,000 bodies a day - hoping to increase this to 6,000 so that all corpses will be buried within the next five days.
The first contingent of US marines is scheduled to arrive in Sri Lanka on Sunday from a base in Okinawa, Japan, launching what will be the American military's largest-ever operation in Asia since the Vietnam War.
More than 1.8m people will have to be fed for months, says the UN
Up to 1,500 US troops are to be deployed in government-run areas of the country, where some of the tsunami damage was caused in areas controlled by Tamil Tiger rebels.
The marines will have 10 helicopters and two C-130 planes to distribute basic supplies to survivors.
A UN special envoy, Margarita Walstrom, said after a visit to Sri Lanka that there were no signs yet of disease but medical staff were anxious about sanitation.
In India, emergency personnel have now reached the most remote locations in the Andaman and Nicobar islands.
The runway at the tsunami-ruined air force base at Car Nicobar is barely serviceable but the military is now managing to fly in plane-loads of desperately needed water and food.
The BBC's Jonathan Charles reports from the island that he saw one coastal village, Malaka, where there was nothing but ruins. Every house had been crushed by the wall of water.