Many children were swept away as they played on beaches

Some were too weak to cling on to their families, homes or trees as huge waves struck countries including Sri Lanka, Thailand, India and Indonesia.

Others could not run fast enough to outpace the rushing water which flooded villages and beaches where they played.

For the survivors, many now orphaned, disease poses the biggest threat.

Witnesses described seeing children pulled under water by the waves, said Carol Bellamy, executive director of the UN children's agency Unicef.

"Kids can run fast but they were least able to withstand the flooding or hold on," she said. "So that is one of the reasons children have been particularly affected."

People were screaming and kids were screaming all over the place, screaming 'help, help'. And after a few minutes you didn't hear the kids any more Czech model Petra Nemcova

Young people are also likely to make up a large share of the casualties because they represent 39% of the population in the hardest-hit countries, Unicef said.

Even the timing of the tsunamis, which struck when schools were closed, may swell the proportion of children among the more than 110,000 killed.

Laura Conrad of the UK charity Save the Children said: "Lots of children on that Sunday morning would have been playing along the beaches and were just swept away.

"They wouldn't have been strong enough to grab hold of things and wouldn't have been able to swim against the tide."

'Enormous task'

Czech model Petra Nemcova told the New York Daily News how a wall of water hit the Thai resort of Khao Lak.

"People were screaming and kids were screaming all over the place, screaming 'help, help'. And after a few minutes you didn't hear the kids any more."

CONFIRMED DEATH TOLL Sri Lanka: 21,715 Indonesia: 32,828 India: 6,974 Thailand: 1,516 Maldives: 52 Malaysia: 44 Burma: 30 Bangladesh: 2 Somalia: 100 Kenya: 1 Seychelles: 3 Tanzania: 10 World's worst disasters At-a-glance: Countries hit

Ms Conrad told the BBC News website that the aid workers' immediate aim was to ensure surviving children had clean water, food, shelter and medical assistance.

Many have been separated from their parents or orphaned by the floods.

"We are working to help them trace their families but clearly it is an enormous task," Ms Conrad said.

Lizette Burgers, of Unicef India, described how poverty-stricken fishing villages in India's Tamil Nadu region were struggling to cope.

"I have talked to mothers who are desperately searching for their children but cannot afford a bus ticket to visit nearby villages to look for them," she said.

"There is no doubt we will need to focus on water and hygiene and there are many children who are traumatised."

Aid agencies fear children will be vulnerable if disease spreads

Unicef has already flown emergency health supplies for more than 150,000 people to Sri Lanka, and the World Health Organization (WHO) is sending medical kits across the region.

Save the Children teams are delivering food and medicine to 37,000 families in Sri Lanka and handing out children's clothes and plastic sheeting in Indonesia.

Children crowded into temporary camps will be particularly susceptible to acute respiratory infections, diarrhoea and waterborne diseases like typhoid and cholera, the WHO said.

The UN Population Fund warned many more women and girls might die in childbirth or lose their children as a result of disease, trauma and damage to the healthcare infrastructure.

HOW YOU CAN HELP Click below to visit the websites of agencies carrying out relief work Cafod Care International International Federation of the Red Cross Medecins Sans Frontieres Oxfam Save The Children Unicef World Vision Disease 'could swamp zones'

But among all the deaths and misery, there are some stories of miraculous escapes from the waves.

One 13-year-old girl survived after spending two days clinging to a wooden door in the Indian Ocean after being swept from an Indian air force base on the remote Car Nicobar island.

Locals found Meghna Rajshekhar walking along a beach in a daze after she had drifted for 48 hours in water teeming with snakes and turtles, officials said.

Six-year-old Yeh Chia-ni from Taiwan, who was holidaying in Thailand's Phi Phi island with her parents, clung to a coconut tree for more than 20 hours before she was rescued.

And a four-year-old boy in southern Thailand was reunited with his parents after spending more than two days on a tree-top without food or water, Reuters news agency reported.