At least 351 people were killed and nearly 100,000 left homeless when tropical cyclone Nargis tore through Myanmar, razing thousands of buildings and knocking out power lines, state media said Sunday.

Residents awoke Sunday to scenes of devastation after the cyclone bore through swathes of southern Myanmar late Friday and Saturday, uprooting trees, cutting phone lines and water pipes, and clogging streets with debris.

Myanmar's state channel MRTV said on their Sunday evening news broadcast that 109 people had been killed in Haing Gyi island, just off the coast of southwestern Ayeyawaddy division where the storm first hit.

One person was killed in Nyaung Done, a township also in Ayeyawaddy, the channel reported.

An information ministry official and state media had already reported that another 222 people had died in Ayeyawaddy, while 19 others were killed in the economic hub Yangon.

The authorities have declared disaster zones in the regions of Yangon, Ayeyawaddy, Bago, Mon and Karen states.

MRTV said that about 20,000 houses have been destroyed on Haing Gyi island, and 92,706 people there were now homeless.

In one mainland township in Ayeyawaddy, 75 percent of all homes were believed to be destroyed, the channel said, adding that authorities had launched a rescue operation in the region.

Nargis made landfall late Friday around the mouth of the Ayeyawaddy (Irrawaddy) river, about 220 kilometres (137 miles) southwest of Yangon, before hitting the country's economic hub.

The cyclone brought down power and phone lines, cutting off the military-run nation one week before a crucial referendum on its new constitution -- the first polling in Myanmar since general elections in 1990.

The coastal area of Ayeyawaddy appears worst hit by the natural disaster, but Yangon was also battered.

Traffic lights, billboards and street lamps littered the roads after being knocked over by strong winds.

Trees in the leafy city were uprooted, crushing buildings and cars, while water pipes were also cut, forcing people out onto the streets with buckets to try and buy water from the few shops that remained open.

Roofs of houses have been torn away, while only a few taxis and buses -- which tripled their fares -- braved the debris-clogged streets on Sunday.

The information ministry official said seven empty boats had sunk in the country's main port, while Yangon's international airport was closed.

State media said the airport was due to reopen on Monday.

"Now the military and police have started to clean the city," the official said. "We are trying to get back to the normal situation as soon as possible."

Electricity supplies and telecommunications in Yangon have been cut since late Friday night as the storm bore down from the Bay of Bengal, packing winds of 190-240 kilometres (120-150 miles) per hour.

There are also fears that the poorer outlying areas of Yangon, with their flimsy houses, might have been hard hit.

"A tea shop owner told me that many people in a Yangon suburb need urgent help for food and accommodation," one food vendor said. "Some children are not even wearing clothes."

Myanmar's infrastructure has been run into the ground by decades of mismanagement by the military, which has ruled since 1962.

It was not immediately known whether damage from the storm would affect next Saturday's referendum on a new constitution, which the ruling junta says will pave the way for democratic elections in 2010.

Critics, however, say the charter will simply enshrine the military's power.

Residents in Yangon said they had heard speculation that the referendum might be postponed, but the information ministry official refused to comment.

"We cannot say anything, it is up to the senior authorities," he said.

Thailand's meteorological department downgraded Nargis to a depression on Sunday, but warned of flash floods and heavy rains in northern, central and eastern Thai provinces as the storm crept over the border from Myanmar.

An official at Thailand's disaster prevention department told AFP that as of Sunday evening, there were no reports of severe flooding in the kingdom.