Even before you set foot in Burma, as the aircraft begins its descent towards Rangoon airport, it is obvious that something appalling has happened. Usually, the Irrawaddy delta is a land of deep and varied greens — the rice and vegetable fields, the river banks and the tropical trees that shade the towns and villages. But today the landscape is dominated by a different colour — the thick enveloping brown of river mud.

It fills the swollen rivers and creeks and lies in a sticky blanket over vast areas of rice paddy. Ponds have been turned into brown lakes, meadows have become marshes and somewhere down there are millions of people whose lives were overturned on Saturday by a rising tide of brown water.

Every day, the extent of the destruction caused by Cyclone Nargis has been revised upwards, from alarming to grim to disastrous — and yesterday it became clear that this is not just a local, but an historic catastrophe. Foreign aid workers in Rangoon have concluded that as many as 50,000 people died in last Saturday’s cyclone, and two to three million are homeless, the worst disaster in the country’s modern history, and of a scale comparable with the 2004 Indian Ocean tsunami.

The people’s plight is not helped by the disposition of their Government. Running the country on a combination of internal repression and xenophobia, the junta seems not to have made up its mind that this is a tragedy that it cannot remedy on its own.

It certainly was not too concerned when the cyclone approached the Burmase coast. A spokesman for the Indian Meteorological Department revealed yesterday that it had given Burma two days’ warning of Cyclone Nargis. “Forty-eight hours before Nargis struck, we indicated its point of crossing \, its severity and all related issues to Burmese agencies,” he said. Weather systems in the Bay of Bengal are tracked by India by satellite.

As the generals dithered, President Bush made a direct appeal to the regime yesterday, urging it to open up to foreign aid and offering the assistance of the US Navy, which had two ships within two days’ sailing time of Burma. Bernard Kouchner, the French Foreign Minister, accused the junta of placing conditions on aid. Britain pledged £5 million and offered an emergency field team to the country.

The latest official death toll was 22,500, according to Burmese state media. But even after three days there has been no comprehensive survey. Assuming that there are many casualties to be revealed, and that a significant proportion of the 41,000 listed as “missing” are dead, the final toll will be much higher.

“We’re looking at 50,000 dead and millions of homeless,” Andrew Kirkwood, country director of the British charity Save The Children told The Times. “I’d characterise it as unprecedented in the history of Burma and on an order of magnitude with the effect of the tsunami on individual countries. There might well be more dead than the tsunami caused in Sri Lanka.”

In New York yesterday, the Burmese Government formally asked the UN for help. But in other ways it remains resistant to the most obvious and basic assistance. According to its own figures at least 10,000 died in one obscure town alone, Bogalay, 75 miles southwest of Rangoon.

Seven townships have been designated as “priority one” disaster areas, because between 90 and 95 per cent of the buildings have been destroyed. “Anything less than 60 per cent destroyed is not being counted as a priority at this stage by the Government,” Mr Kirkwood said. “That gives some indication of the scale of the problem.”

And yet three days after the cyclone, which swept the Irrawaddy delta with winds as high as 160mph and drove before it a storm surge 7.5 metres high, there is still no co-ordinated relief effort. Last night, the UN World Food Programme said that it had begun distributing food in hard-to-reach areas, but the difficulty of providing prompt and meaningful assistance remains a key concern.

Even as the cyclone was blowing itself out, the UN’s acting boss in Rangoon, Chris Kaye, was pressing the Government to receive a humanitarian team trained to make rapid judgments about the needs of survivors. Yesterday, permission had still not been granted.

UN and charity staff are still waiting for visas to enter Burma. Foreign journalists are barred from openly operating and the thinness of press and television coverage makes it all the harder for charities to raise money.

The sheer physical difficulties of penetrating the delta region pose another problem. Three million people live there but with few roads and much water, transport has always been slow, relying on boats that travel the rivers, canals and channels known as the “mouths of the Irrawaddy”. The cyclone destroyed an uncounted number of boats, as well as inundating roads and tracks.

Short distances from Rangoon, the biggest city, and home to most of its expatriate aid workers, are towns where almost no houses remain, where people are living in the open without clean water, power or food. The few aid workers who have overflown the stricken areas in military helicopters report corpses clogging the fields. The human need is acute and yet no one with the capacity to provide full and co-ordinated help can get near. Reflecting the scale of the crisis, the junta said that it would postpone in the worst-hit areas a constitutional referendum — the “roadmap to democracy” — but the rest of the nation would vote as planned on Saturday.

Even in Rangoon, which came off relatively lightly, the extent of the destruction is breathtaking. Every road in the city is littered with fallen trees. The lightest houses, of wood and corrugated iron, blew away; heavier ones sustained broken windows, lost tiles and were damaged by trees that crashed into them like battering rams.

The people hurt the most are the people who began with the least. In North Okkalopa township, the usually sluggish Nga Moe Yeik creek turned into a torrent and washed away parts of the shantytowns on its banks, forcing thousands to take shelter in two schools. Many work as day labourers in factories in other parts of the city but the cost of fuel means that the bus fare now exceeds the daily wages.

Thousands of cars form half-mile queues across the city, waiting up to six hours for the ration of two gallons of petrol. Few people have water, because the electricity that drives the pumping stations is down. At night the few big hotels and expatriate apartments fire up lights from generators. Elsewhere and far down through the delta to the Andaman Sea: darkness.

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