Aid agencies and Western countries are stepping up efforts to help survivors of the Indian Ocean sea surges, as the death toll rises towards 70,000.
Health experts fear disease could double the death toll
The US has more than doubled its pledge of funds to $35m. Two flotillas of US warships with 15,000 troops are carrying relief supplies to the region.
Many other governments and bodies - including Canada, Australia, European countries and the UN - are sending aid.
The UN says disease could double the death toll after Sunday's earthquake.
India says it will install an early warning system to predict tsunamis.
Officials and scientists have suggested that many of the casualties could have been avoided if a system such as the one used in Pacific Rim countries was in operation.
The 9.0 magnitude earthquake happened just off the coast of the Indonesian island of Sumatra early on Sunday, and set off huge waves that reached as far as Africa.
On Wednesday the UK government pledged £15m ($29m) to help the first phase of the relief effort - making Britain the second largest donor after the US.
The American military says it has diverted an aircraft carrier, as well as other ships and at least 20 aircraft, to affected countries.
Meanwhile German Chancellor Gerhard Schroeder has called for a moratorium on debt repayment for two of the affected nations, Somalia and Indonesia.
Full horror emerges
In Indonesia, thousands of troops have been drafted into the north-western province of Aceh to dig mass graves.
The BBC's Rachel Harvey in the provincial capital, Banda Aceh, says that in the space of 20 minutes she counted 10 lorries filled with bodies arriving at one grave.
The first ship carrying emergency supplies is reported to have reached the worst hit town of Meulaboh, where 10,000 are feared dead, 10% of the population.
But many areas along the western coast of Sumatra have still not been reached.
As relief workers across the region recover more bodies from beaches and collapsed buildings, the true extent of the devastation is becoming clearer:
- The official Indonesian death toll stands at about 36,268 - but a UN official estimated that it could reach between 50,000 and 80,000.
- At least 7,000 are feared dead in India's Nicobar and Andaman islands, which have been laid waste by the tsunami and at least three aftershocks. A police chief who has flown over the stricken areas said one in five of the islanders were either dead, missing or injured
- In Thailand more than 1,500 have been confirmed dead, including at least 473 foreign tourists staying at beach resorts - the Thai government says the total death toll may rise to 2,000
- Unicef warns that children could account for up to a third of the dead.
Plane loads of supplies are also arriving in Sri Lanka - the worst-affected country outside Indonesia, with more than 21,000 confirmed dead.
A UN team is also on the island to co-ordinate the relief effort.
But the BBC's Roland Buerk on the southern coast says getting the aid to the worst-hit areas will be a huge logistical operation.
The Tamil Tiger rebels - who control large stretches of affected coast in the north - say that so far they have received no help from the authorities.
The Sri Lankan government has urged people to put aside divisions to rebuild the country and President Chandrika Kumaratunga has declared Friday a day of national mourning.
The UN has said it faces an unprecedented challenge in co-ordinating distribution of aid to some 10 nations at once.
In Geneva, World Health Organization expert David Nabarro has warned "there is certainly a chance that we could have as many dying from communicable diseases as from the tsunami".
IMPACT OF THE EARTHQUAKE