YANGON (Reuters) - A powerful cyclone that slammed into Myanmar's Irrawaddy delta triggered a massive wave that gave people nowhere to run, killing at least 15,000 and leaving 30,000 others missing, officials said on Tuesday.

"More deaths were caused by the tidal wave than the storm itself," Minister for Relief and Resettlement Maung Maung Swe told a news conference in the devastated former capital, Yangon, where food and water supplies are running low.

"The wave was up to 12 feet high and it swept away and inundated half the houses in low-lying villages," he said, giving the first detailed description of the weekend cyclone. "They did not have anywhere to flee."

It is the worst cyclone to hit Asia since 1991, when 143,000 people died in Bangladesh.

Information Minister Kyaw Hsan said the military were "doing their best," but analysts said there could be political fallout for military rulers of the former Burma who pride themselves on their ability to cope with any challenge.

"The myth they have projected about being well-prepared has been totally blown away," said political analyst Aung Naing Oo, who fled to Thailand after a brutally crushed 1988 uprising. "This could have a tremendous political impact in the long term."

Earlier, Foreign Minister Nyan Win said on state television that 10,000 people had died just in Bogalay, a town 90 km (50 miles) southwest of Yangon.

Reflecting the scale of the disaster, the ruling junta said it would postpone to May 24 a constitutional referendum in the worst-hit areas of Yangon and the sprawling Irrawaddy delta.

However, state TV said the May 10 vote on the charter, part of the army's much-criticized "roadmap to democracy," would proceed as planned in the rest of the southeast Asian nation, which has been under army rule for the last 46 years.

The military's political plans have been slammed by Western governments, especially after the army's *lo**y suppression of Buddhist-monk led protests last September.

SEVERAL HUNDRED THOUSAND HOMELESS

The government also lifted states of emergency in three of the five states declared official disaster zones and some parts of the worst-hit Yangon and Irrawaddy regions.

The Information Minister said the government had sufficient stocks of rice despite damage to grain stored in the huge delta, known as the "rice bowl of Asia" 50 years ago when Burma was the world's largest rice exporter.

After a meeting with Myanmar's ambassador to Bangkok, Thai Foreign Minister Noppadol Pattama said he had been told 30,000 people were missing after Cyclone Nargis.

"The losses have been much greater than we anticipated," he said. Ambassador Ye Win declined to speak to reporters.

The total left homeless by the 190 km (120 miles) per hour winds and storm surge is in the several hundred thousands, United Nations aid officials say.

The disaster drew a rare acceptance of outside help from the diplomatically isolated generals, who spurned such approaches in the aftermath of the 2004 Indian Ocean tsunami.

Bernard Delpuech, a European Union aid official in Yangon, said the junta had sent three ships carrying food to the delta region. Nearly half the country's 53 million people live in the five disaster-hit states.

Army-controlled media have made much of the military's response, showing footage of soldiers manhandling tree trunks or top generals climbing into helicopters or greeting homeless storm victims in Buddhist temples.

But with many people still furious at the September crackdown, there is an inevitable sense of the army failing to do enough.

"The regime has lost a golden opportunity to send the soldiers as soon as the storm stopped to win the heart and soul of people," one retired civil servant told a Reuters.

"But where are the soldiers and police? They were very quick and aggressive when there were protests in the streets last year," he said.

"MASSIVE, TERRIBLE"

Aid agency World Vision in Australia said it had been granted special visas to send in personnel to back up 600 staff in the impoverished Southeast Asian country.

"This is massive. It is not necessarily quite tsunami level, but in terms of impact of millions displaced, thousands dead, it is just terrible," World Vision Australia head Tim Costello said.

"Organizations like ours have been given permission, which is pretty unprecedented, to fly people in. This shows how grave it is in the Burmese government's mind," he said.

The town-by-town list of dead and missing announced by Nyan Win, a major-general, showed 14,859 deaths in the Irrawaddy area and 59 in and around Yangon, the country's biggest city.

Residents of the city of 5 million were queuing up for bottled water and there was still no electricity four days after the cyclone struck.

Prices of food, fuel and construction materials have skyrocketed, and most shops have sold out of candles and batteries. An egg costs three times what it did on Friday.

"Generators are selling very well under the generals," said one man waiting outside a shop.