REUTERS, YANGON - A tropical cyclone slammed into Myanmar's main city on Saturday, ripping off roofs, felling trees and power lines and forcing the military authorities to close the airport.

The electricity supply -- hit-and-miss at the best of times in one of Asia's poorest countries -- failed after Cyclone Nargis, packing winds of up to 120 mph, first started to lash the former capital on Friday evening.

There were no reports of deaths, although meteorological officials in the former Burma said the cyclone could trigger a storm surge of up to 3.5 metres in coastal areas.

State-run MRTV and Yangon City Radio were off the air, as were the normally shaky Internet services. Buses and trains were not operating due to extensive flooding in residential areas of the city, which sits on the floodplains of the mighty Irrawaddy river.

The damage appeared so extensive it could be several days before power, telecommunication and transport services are up and running, possibly affecting a referendum on a controversial army-drafted constitution scheduled for May 10.

An official at Yangon International Airport said all incoming flights had been diverted to the second city of Mandalay, in the middle of the southeast Asian nation, and all departures from Yangon had been cancelled.

However, an official at Thai Airways in Bangkok said the airline planned to resume flights on Sunday, although was unable to give any details of conditions on the ground in Myanmar.

Myanmar weather officials said Nargis was expected to keep moving northeast from Yangon and cross in the next 24 hours into northern Thailand, where a storm warning has already been issued. Heavy rain is expected to cover much Thailand until Monday, the weather bureau said.