They fear more isolated villages along the west coast of Indonesia's Aceh province where most of the country's 104,055 deaths occurred could still be fending for themselves.
In Aceh, where aftershocks from the undersea earthquake on 26 December that spawned the huge waves continued to be felt on Sunday, many communities remain inaccessible by land and are dependent on food aid dropped by helicopter.
"People in helicopters say they've seen people presumably walking to Banda Aceh (the provincial capital) and living on coconuts," Maria Theresa De la Cruz, head of relief operations for Aceh in the International Organisation for Migration (IOM), said.
IOM is coordinating airdrops with the US navy.
The UN World Food Programme's spokesman in Jakarta, Mike Huggins, added: "I'm not saying everyone is getting food. The vast majority of people who need food are getting it although maybe not enough."
Chris Lom, spokesman for IOM in Indonesia, said, "That's what a lot of people are worried about. A serious assessment hasn't been done."
While the world has promised more than $4 billion to help Asia recover from the disaster, some shattered survivors say the money needs to start filtering through to them now.
"My life is in a mess now. Unless aid funds come to us directly and quickly, we may all have to bury ourselves together with the dead," a tired Anita said while lining up to collect a bowl of rice and potato at a Banda Aceh relief centre.
On Saturday the UN again urged donor countries to quickly come up with the cash they have pledged.
Annan has visited Indonesia and
Sri Lanka on a fact-finding trip
"The watchword is cash," Elisabeth Byrs, a spokeswoman for the UN's humanitarian coordination agency, said from Geneva.
The current EU president, Luxembourg Prime Minister Jean-Claude Juncker, told French radio on Sunday he favoured "full debt relief" for countries hit by the tsunami disaster.
"Personally, I'm in favour of full debt relief for these countries," he told France Inter Radio, three days before government creditors in the Paris Club are to meet here to consider a debt moratorium for Sri Lanka and Indonesia, two of the countries worst affected by the devastating waves.
Oil-rich Kuwait became the latest country to increase its aid, raising its aid pledge for Asia's tsunami victims tenfold to $100 million.
But despite the global outpouring of funds, questions of distribution, logistical coordination and even politics continue to hang over recovery efforts expected to last years, and officials acknowledge they were not sufficiently prepared for a disaster of this scale.
Colombo objected to Annan's
visit to Tamil Tiger-held areas
"Right now we are trying to get control of this," Andrew Natsios, administrator of the US Agency for International Development, said.
"I think there will be a lot of case studies done and a few lessons drawn."
EU's response to the disaster has turned the spotlight on the gap between its formidable financial might - billions of dollars in aid have been pledged - and its limited capacity to act fast and in a coordinated fashion on the ground.
"I concede that Europe did not show exemplary logistical efficiency. It is not a criticism, just a fact," French Health Minister Philippe Douste-Blazy said on his return from Asia.
Local insurgencies also continue to be serious complications in efforts to help Indonesia, where the government said 77,000 people remain missing on Sumatra island, and Sri Lanka.
Rights groups have warned Jakarta's military campaign to crush a long-running rebellion in Aceh and restrictions on aid groups were hindering relief efforts.
Insurgencies in the region have
complicated aid-delivery effort
In Sri Lanka where at least 30,718 people died, a bitter row erupted over aid distribution, with Tamil Tiger rebels accusing government soldiers of diverting relief away from the north and eastern areas they control.
The government denies the charge.
As he wrapped up a two-day tour of tsunami-ravaged areas of the island on Sunday, UN chief Kofi Annan said he wanted to return to "see all parts of the country" amid reports the government blocked him from visiting rebel-held northern areas.
"I'm hoping to come back ... and see all parts of the country and be of help to accelerate the peace process," Annan said.
Later in the evening, he arrived in the Maldives, which was also hit by the giant waves.
The Sunday Leader newspaper said President Chandrika Kumaratunga had personally objected to an on-site visit by Annan to zones held by the rebel Liberation Tigers of Tamil Eelam (LTTE), fearing they would make political capital out of it.
Colombo insisted the programme had been worked out with UN officials, who had been offered stopovers in the north.
Annan met on Sunday with members of the Tamil National Alliance, regarded as proxies of the Tamil Tigers, and leaders of other political parties in a meeting chaired by Kumaratunga.
Donations from the Gulf states
have jumped in the past week
After touring Sri Lanka with Annan on Saturday, World Bank president James Wolfensohn said his organisation could raise its financial aid to tsunami-hit Asian regions to $1 billion, from its initial $250 million.
India, meanwhile, said on Sunday it will set up an early warning system and disaster management authority amid criticism it is not doing enough for people orphaned or made homeless by the tsunami disaster.
The decision came a day after Prime Minister Manmohan Singh unveiled a $45.7 million package for the Andaman and Nicobar Islands.
Some 1205 people were confirmed dead and 5531 are still missing and feared dead on the Andamans, which lay close to the epicentre of the underground earthquake off Sumatra island.
Death toll rises
The overall death toll in India is at least 10,022 people killed and 5617 missing, most feared dead.
In Thailand, the nationalities of bodies hastily buried after southern resort areas were pummelled were cast into doubt Sunday, with the interior ministry saying initial visual identification of 1973 corpses has proved unreliable.
Of the 5305 people killed, 1792 are believed to be of Thai and 1329 of foreign origin, the division said. The national origin of the rest was uncertain.
Interior Minister Bhokin Bhalakula has reportedly ordered autopsies on 600 corpses from Bang Maruan cemetery in the devastated Phang Nga province, after relatives complained victims were buried without being properly identified.
Stream of visitors
The doubts came as a stream of foreign dignitaries visited Thailand to check on the international forensics effort, and offer aid.
On Sunday German Foreign Minister Joschka Fischer travelled to Wat Yanyao in Phang Nga, which suffered most of Thailand's casualties, before returning to the tourist island of Phuket to meet with Thai and international officials.
Foreign ministers from Britain, Canada, Japan, Norway have come since Friday, and their Spanish counterpart is also expected.
Thailand said it will host a regional ministerial meeting this month on a tsunami early warning system for the Indian Ocean.