The city of Rangoon was a disaster zone yesterday after a devastating cyclone blew away houses, tore down trees and power lines and killed more than 350 people in Burma.

In some towns south of Rangoon three quarters of the houses were reported to have been destroyed by a combination of wind, rain and a storm surge which inundated the delta of the Irrawaddy, the river that sustains the livelihoods of millions of people in one of Asia’s poorest nations.

According to state television at least 19 people died in Rangoon, and more than 220 in the Irrawaddy division, a low-lying area where much of Burmese rice is grown. Efforts to determine the extent of the damage have been frustrated by blocked and flooded roads and broken telephone lines.

The death toll is likely to climb as the authorities re-establish contact with outlying islands and villages that bore the full force of Cyclone Nargis, a Category 3 storm with winds of 190 km/h (120mph). Foreign aid workers, their movements restricted by the ruling junta, struggled to reach many afflicted areas to assess the impact. “I have never seen anything like it,” a retired government worker said. “It reminded me of when Hurricane Katrina hit the US.”

Rangoon airport was closed yesterday and flights were being diverted to Mandalay, in the centre of the country. An official state of emergency was declared in the Irrawaddy, Bago, Mon and Karen divisions. The disaster comes at a sensitive time. After 46 years of totalitarian rule, and brutal suppression of the opposition, the junta planned to hold a referendum next Saturday on a new constitution.

The Government promises free elections in 2010. But Burmese opposition groups insist that the constitution is a sham that will simply transfer power from uniformed officers to besuited military toadies. The new constitution guarantees a quarter of all seats for the military and bars the Nobel Prize winning opposition leader, Aung San Suu Kyi, from the presidency.

Ms Suu Kyi’s opposition National League for Democracy is urging Burmese to reject the referendum while the Government is mobilising its own grassroots support organisations to vote “Yes”. Last night, there was no official suggestion that the cyclone would affect the referendum, but if communications remain seriously disrupted it must be in doubt.