An Indian man cries as he holds the hand of his eight-year-old son killed in a tsunami in Cuddalore near the Indian city of Madras. Picture / Reuters

An Indian man cries as he holds the hand of his eight-year-old son killed in a tsunami in Cuddalore near the Indian city of Madras. Picture / Reuters

The death toll from the tsunami which devastated coastal areas of South East Asia was about 23,200 today as the United Nations warned it could be the worst natural disaster of modern times.

More than two million people lost their homes and tens of thousands were injured with many more still unaccounted for after the flash floods triggered by a massive under-sea earthquake off Sumatra in Indonesia.

With huge numbers of bodies left to rot in the tropical sun, aid agencies warned of cholera and dysentery epidemics as local officials struggled to cope with scale of the disaster. Villages, towns and cities across the region held mass burials as bodies piled up on the beaches unclaimed.

Tens of thousands of tourists were trying to get out of the region as it emerged that dozens of holidaymakers, including 13 Britons, had lost their lives in the Boxing Day disaster. Most of them were killed in Thailand and Sri Lanka.

Britain's Foreign Secretary Jack Straw warned the final number of British casualties is likely to be much higher.

A Foreign Office spokeswoman said there was no news about the whereabouts of a group of 50 British teachers who were on holiday in the south of Sri Lanka.

There were a further 14 aftershocks yesterday as fears mounted for the inhabitants of the remote Andaman and Nicobar Islands where contact has been lost and tens of thousands are now feared dead. A $3.8 billion secret military base on the archipelago, thought to garrison up to 8,000 soldiers, was swept away when the waves struck, a senior Indian official told the Independent.

Hundreds of people also died and entire villages and towns disappeared in Somalia on the east coast of Africa - the furthest point from the epicentre. Meanwhile, governments were accused of doing too little to warn their populations of the impending waves and there were calls for an international seismic monitoring system to prevent a repeat of the tragedy.

UN Emergency Relief Co-ordinator Jan Egeland said the effects of the disaster would be particularly dramatic because so many of the places hit had large, poor populations, crammed into substandard housing.

"This may be the worst natural disaster in recent history because it is affecting so many heavily populated coastal areas ... so many vulnerable communities," he said.

The Geneva-based International Federation of the Red Cross and Red Crescent Societies said it would need $6.5m to begin emergency assistance. The United States dispatched disaster teams and prepared a $15m aid package to the Asian countries.