The known toll stands above 50,000 but estimates suggest thousands more are dead, many of them children.
Two US warships carrying some 15,000 soldiers and cargo aircraft with supplies are en route to the region, as part of a massive global relief effort.
The UN has warned disease could double the death toll from Sunday's quake.
The 9.0 magnitude earthquake happened just off the coast of the large Indonesian island of Sumatra, and set off huge tsunami waves that reached as far as Africa.
Indonesia, Sri Lanka, India and Thailand are among the countries worst hit.
Click here for map of affected area
Full horror emerges
Across the afflicted region, searches are continuing to uncover bodies from beaches and collapsed buildings.
In India, Indonesia and Sri Lanka, bodies are being buried as quickly as possible in mass graves, and hospitals and aid agencies are scrambling to cope.
CONFIRMED DEATH TOLL
Sri Lanka: 18,706 dead
Indonesia: 27,174 dead
India: 4,371 dead
Thailand: 1,516 dead
Maldives: 52 dead
Malaysia: 44 dead
Burma: 30 dead
Bangladesh: 2 dead
Somalia: 100 dead
Kenya: 1 dead
Seychelles: 3 dead
Tanzania: 10 dead
World's worst natural disasters
At-a-glance: Countries hit
In several of those nations, some outlying towns and villages have not yet even been reached.
But as rescue workers discover more bodies, the true extent of the tsunami's devastation is becoming clearer:
- The official Indonesian death toll stands at 27,174 - but the vice-president estimated the real tally was 30,000 to 40,000. Officials have estimated the inundated Sumatran town of Meulaboh may have lost 10,000 inhabitants - about 10% of its population
- Parliamentary elections in the Maldives, scheduled for Friday, are postponed, as a government official warns the cost of damage could exceed the island nation's annual GDP
- About 7,000 people are feared dead in the low-lying Andaman and Nicobar islands, say Indian officials, with 20% of the population on one island, Car Nicobar, believed killed
- The bodies of more than 700 mainly foreign tourists have been found in the Thai resort of Khao Lak - the government says the death toll in Thailand may rise to 2,000
- Unicef warns that children could account for up to a third of the dead.
But there have been some stories of survival against the odds. A four-year-old boy was reunited with his parents in Thailand after a giant wave left him stranded in a tree for two days without food or water, Reuters news agency reported.
The UN has said it faces an unprecedented challenge in co-ordinating distribution of aid to some 10 nations at once.
HOW YOU CAN HELP
Click below to visit the websites of agencies carrying out relief work
International Federation of the Red Cross
Medecins Sans Frontieres
Save The Children
Disease 'could swamp zones'
The worst-affected countries have been overwhelmed by the scale of the disaster - a disaster compounded because infrastructure was also knocked out.
In Geneva, World Health Organization (WHO) expert David Nabarro has warned "there is certainly a chance that we could have as many dying from communicable diseases as from the tsunami".
US cargo aircraft are among hundreds of planes expected to arrive in the next few days.
The US has more than doubled its aid pledge to $35m but denies this is in response to remarks from the UN emergency relief co-ordinator Jan Egeland that rich nations were "stingy" in pledging relief funds.
Coastal communities across South Asia - and more than 4,000 km away in Africa - were swept away and homes engulfed by waves up to 10m high after the quake created a tsunami that sped across the ocean.
Sunday's tremor - the fourth strongest since 1900 - had a particularly widespread effect because it seems to have taken place just below the surface of the ocean, analysts say.
Tsunamis generated by earthquakes can travel at up to 500km/h.