Aid agencies are calling for speedy access to survivors as the scale of the disaster in Burma in the wake of Cyclone Nargis becomes apparent.
Hundreds of thousands of survivors face disease and hunger.
Tens of thousands of people have been killed and up to a million are without shelter in the Irrawaddy delta region.
A BBC reporter who has managed to get into the tightly controlled country says the government seems more inclined to manage information than bring aid.
UN agencies, meanwhile, are negotiating for access.
The work of international agencies is restricted in Burma but there are some indications that the disaster may bring more flexibility from the government.
Richard Horsey, a spokesman for the UN's disaster relief agency OCHA said that the Burmese government had named Deputy Foreign Minister Maung Myint to oversee visa applications for aid agencies.
"The appointment of someone at ministerial cabinet level on these things, we hope, will start to move things quickly," he told the French news agency AFP.
Reports from Geneva, meanwhile, say that Burma has agreed to allow in a UN flight carrying emergency supplies.
'Time of the essence'
Andrew Kirkwood, Burma country director for Save the Children, said the situation in the country was urgent.
"In some areas we know that the areas are still completely under water, under salt water... some people have absolutely no drinking water and food.
"Unless assistance gets into those kinds of areas very soon, the death toll will rise."
"We are still thinking positively that we will be able to reach everyone, but it is a race against time at the moment."
The UN agency Unicef warned that survivors faced poor sanitation and a lack of access to clean water, as well as the threat of diseases such as malaria, cholera and dysentery.
"Time is of the essence," Ann Veneman, executive director of the agency said.
"In situations such as these, children are highly vulnerable to disease and hunger and they need immediate help to survive."
Assessment teams are on the ground and in some places aid is beginning to make its way to those who need it.
The World Food Programme has begun to distribute food in and around Burma's main city, Rangoon.
But parts of the low-lying Irrawaddy delta region remain isolated and aid experts are warning that a massive logistical effort will be required to assist people there.
Details are continuing to emerge of the destruction caused by the cyclone, which caused a sea surge 12 ft (3.5m) high.
Satellite images released by the US space agency, Nasa, showed virtually the entire coastal plain of the country under water.
Swathes of southwest Burma are under water following the cyclone
Some 95% of the homes in the city of Bogalay were destroyed and most of its 190,000 residents are reported to be homeless. The neighbouring cities of Labutta and Pyapon have also been badly affected.
Mr Kirkwood said his staff had witnessed harrowing scenes in worst-hit parts of the region.
"One team came across thousands of people killed in one township, with piles of rotting bodies lying on the ground as the water had receded," he said.
State media reported on Tuesday that 22,464 people had now been confirmed dead and another 41,054 people missing as a result of the cyclone.
As rescue teams get to areas presently cut off, those figures are expected to rise.