YANGON, MYANMAR - HUNDREDS of thousands of people have been left without shelter and drinking water in military-ruled Myanmar after a devastating cyclone tore through the Irrawaddy delta, a United Nations official said on Monday.

'We know that it's several hundred thousand needing shelter and clean drinking water, but how many hundred thousand we just don't know,' Mr Richard Horsey, of the United Nations disaster response office in Bangkok, told Reuters.

Tropical Cyclone Nagris has killed more than 350 people and destroyed thousands of homes in Myanmar, state-run media said. Some dissident groups worried that the country's military government would be reluctant to ask for international help.

The military government said Saturday's referendum on a new constitution intended to usher in democracy would go ahead, but with food prices tripling and water supplies cut, residents said they had more pressing problems.

'We don't want any democracy, we just want water now,' a 30-year-old man said as he queued at a neighbour's well.

But the junta, based in the remote new capital of Naypyidaw, insisted 'the entire people of the country are eagerly looking forward' to the referendum, the New Light of Myanmar newspaper reported.

Opposition leader Aung San Suu Kyi's house in Yangon, were she is under house arrest, was damaged but the Nobel peace laureate was unhurt, a Myanmar official told AFP.

Some in Yangon complained the 400,000-strong military was doing little to help victims after Saturday's storm.

'Where are all those uniformed people who are always ready to beat civilians?' a trishaw driver, who refused to be identified for fear of retribution, said on Sunday. 'They should come out in full force and help clean up the areas and restore electricity.'

Myanmar, also known as Burma, has been under military rule since 1962. Its government has been widely criticised for human rights abuses and suppression of pro-democracy parties.

Last September, at least 31 people were killed and thousands more were detained when the military cracked down on peaceful protests led by Buddhist monks and democracy advocates.

The Forum for Democracy in Burma and other dissident groups outside of Myanmar urged the military junta Sunday to allow aid groups to operate freely in the wake of the cyclone - something it has been reluctant to do in the past.

It would be difficult for other countries to help unless they received a request from Myanmar's military rulers.

'International expertise in dealing with natural disasters is urgently required. The military regime is ill-prepared to deal with the aftermath of the cyclone,' said Mr Naing Aung, secretary general of the Thailand-based forum.

The storm's 120 mph winds blew the roofs off hospitals and cut electricity to the country's largest city.

Ms Shari Villarosa, the top American diplomat in Yangon, said the storm's whipping winds and torrential downpour had caused 'major devastation throughout the city.'

'The Burmese are saying they have never seen anything like this, ever,' Ms Villarosa said.

'Trees are down. Electricity lines are down. Our Burmese staff have lost their roofs.'

At least 351 people were killed, including 162 who lived on Haing Gyi island off the country's southwest coast, military-run Myaddy television station reported. Many of the others died in the low-lying Irrawaddy delta.

'The Irrawaddy delta was hit extremely hard not only because of the wind and rain but because of the storm surge,' said Mr Chris Kaye, the UN's acting humanitarian coordinator in Yangon.

'The villages there have reportedly been completely flattened.'

State television reported that in the Irrawaddy's Labutta township, 75 per cent of the buildings had collapsed.

The UN planned to send teams on Monday to assess the damage, Mr Kaye said. Initial assessment efforts had been hampered by roads clogged with debris and downed phone lines, he said.