Myanmar's military government declared five disaster areas, including its main city, on Sunday after a large tropical cyclone killed at least four people in Yangon, state newspapers said.

The city was without power and water and the streets were littered with debris from felled trees and battered buildings. Many roofs had been ripped off.

The worst-hit area was the Irrawaddy delta where 50 percent of buildings in some towns had been damaged or collapsed, state media said.

Cyclone Nargis, packing winds of 190 km (120 mile) per hour, ploughed through the heart of the sprawling river delta city of Yangon, home to 5 million people, on Saturday.

Trees and powerlines were ripped up across Yangon and buildings toppled in the posh suburbs surrounding Yangon University, a Thailand-based, anti-regime activist group told Reuters.

Internet, land, mobile and most satellite phone connections have been down since the storm neared the former Burmese capital, making it impossible to confirm the extent of the damage.

The state media reports gave few other details, the British embassy employee said, although she added that by 8.30 am (0200 GMT) on Sunday the rain had passed and the sun was shining.

Kyaw Lin Oo of Thailand-based Burma Democratic Concern, who managed to contact a Yangon colleague on Saturday night, said the whole city was "in a very bad condition".

"All the trees have been uprooted and some buildings have fallen down near Yangon University," he told Reuters in the Thai capital.

On Saturday, a United Nations official in Bangkok said UN staff had spoken to a colleague in Yangon as the eye of the storm passed overhead in the afternoon.

"A lot of roofs from well-constructed buildings have been blown off. That would lead you to believe that less well-constructed buildings will have taken a really big whack," Tony Craig, regional emergency coordinator for the World Food Programme (WFP), told Reuters.

The Federation of Trade Unions, Burma, a Thailand-based labour rights group, said the ruling military junta had declared states of emergency in five affected provinces, most of them in the low-lying floodplains of the Irrawaddy delta.

A spokesman for Britain's Department for International Development (DFID), which has a staff of 10 in Myanmar, said it had not been able to establish the extent of damage because of poor communications, but that its people were safe.

The electricity supply in Yangon -- hit-and-miss at the best of times in one of Asia's poorest countries -- failed after Nargis drew near on Friday evening.

Meteorological officials warned of a possible storm surge of up to 12 feet (3.5 metres) in coastal areas, suggesting tens of thousands of people could be at risk.

The streets of Yangon were virtually deserted, and buses and trains were not operating due to extensive flooding, a Reuters reporter in the city said before his communications were cut off.

A spokeswoman for the U.N. Office for the Coordination of Humanitarian Affairs (OCHA) said the International Federation of Red Cross and Red Crescent Societies (IFRC) in Yangon would meet with the Myanmar Red Crescent on Sunday to assess the damage.

It remains to be seen what impact the storm will have on a referendum on an army-drafted constitution scheduled for May 10.

The charter is part of a "roadmap to democracy" meant to culminate in multiparty elections in 2010 and end nearly five decades of military rule. Critics say it gives the army too much control. - Reuters