With torrential storms approaching, and another possible cyclone developing, Myanmar is on the verge of a major humanitarian crisis, the UN has warned.

Children are at risk not only from malnutrition and disease but, faced with a loss of family members, could also be susceptible to kidnapping and trafficking.

Witnesses said villagers from the lower Irrawaddy Delta were moving north to safety, with many trekking towards the former capital, Yangon, in search of food and shelter. “Millions may be on the move,” said a Western diplomat based in Yangon. “Within an hour’s drive or so from Yangon there are already large groups of people huddled together, squatting by the road, waiting for water and food to reach them.”

“They are understandably trying to escape the devastation,” said Amanda Pitt, the regional communications officer for the UN’s Office for the Co-ordination of Humanitarian Affairs. “This of course makes assessing the needs of the displaced people more difficult and targeting relief even harder.”

Richard Bridal, the regional head of Unicef, warned that children were especially vulnerable.

“Of course, many of the survivors are children and they are in danger of being kidnapped and trafficked,” Mr Bridal said.

“These children are also in danger of suffering from acute malnutrition; they need to be identified and treated – if they are not, they will certainly die.”

Alexander Kreuger, a child protection expert with Unicef in Bangkok, said mass migration increases the danger of children being separated from their parents, “risking sexual harassment and being trafficked”. Although the international community is growing increasingly impatient with the junta’s intransigence to allow in more aid, the UN remains optimistic that things are improving.

“Supplies are getting in and there has been some movement on allowing visas for UN disaster rapid response experts,” said Ms Pitt. “There has been some progress in some areas, but it’s certainly not enough as yet.”

Diplomats in Yangon, however, are less sanguine.

“There needs to be a 20-fold increase in aid and people,” one Western diplomat said.

Logistics – how to transport the supplies from Yangon to the affected areas in the Irrawaddy Delta to the west of the city – remains one of the most immediate problems. There is already a bottleneck at Yangon’s international airport as available equipment is unsuitable for unloading relief supplies and most of it must be lifted off planes by hand.

Getting aid to the affected areas also remains a problem. The UN estimates it has managed to reach 20 per cent of those in need of food and medical supplies. It has a fleet of 30 lorries to transport the goods to the delta, but are constrained by bridges and rivers that make travel there precarious. The government has supplied small boats and two helicopters to help with deliveries.

“We need more helicopters and have located four in the region that could be used, but we’d need to get permission first,” said Marcus Prior, a senior official with the UN World Food Programme.

“It’s difficult to estimate how much logistical support is needed to bring the operation up to speed – but much more than we have available at present.”

The junta remains deeply suspicious of the outside world and has refused to let in foreign experts who specialise in getting aid to disaster victims. Official statements from the regime say Myanmar welcomes aid from anywhere, but only the government is allowed to distribute supplies.

Recently the generals have started to realise that the magnitude of the disaster may be beyond their capacity. In the past two days they have asked for technical help from Bangladesh, China, India and Thailand.

“The regime is anxious to hide the extent of the cyclone damage from the Burmese people,” said Win Min, an independent analyst from Myanmar based in northern Thailand.

“That’s why foreigners are not being allowed in the delta area and any Burmese aid workers or businessmen travelling there are forbidden to carry cameras,” he said.

Independent newspapers in Myanmar, formerly known as Burma, and periodicals have been barred from carrying pictures of the cyclone damage on their front or back covers, according to one local editor.

Coverage of the cyclone by Myanmar’s private media, including the English weekly The Myanmar Times, has been heavily censored. In particular, they have not been allowed to mention that the regime is preventing international aid and disaster experts into the country.

The regime has also been taking credit for the work of other countries. Food packages from foreign governments have been commandeered by soldiers that have stuck labels on them saying they were being presented by particular generals.

There are also reports that aid supplies are being diverted away from the survivors and turning up on the local market. Local community groups who tried to deliver food to poor people in the outlying areas of Yangon have been forcibly stopped and their bags of rice confiscated.

Nearly 125,000 people were killed by the cyclone, according to aid workers assessing the damage done in the Irrawaddy Delta. The UN estimates that a further 100,000 are missing. The government insists the death toll is around 34,000 with about the same number missing.

The UN estimates that more than two million people have been made homeless and are at risk from diseases ranging from dysentery and typhoid and cholera to malaria and dengue fever.