YANGON -- Myanmar raised its death toll from Cyclone Nargis on Tuesday to nearly 22,500 with a further 41,000 missing, nearly all of them from a massive storm surge that swept into the vast Irrawaddy delta.

People walk through a flooded street in Yangon May 6, 2008. [Agencies]

Of the dead, only 671 were in Yangon, and its outlying districts, state radio said, confirming Nargis as the most devastating cyclone to hit Asia since 1991, when 143,000 people died in Bangladesh.

"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 rubble-strewn city of Yangon, where food and water supplies are running low.

"The wave was up to 12 feet (3.5 metres) 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."

Information Minister Kyaw Hsan said the military were "doing their best".

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 government said it would postpone to May 24 a constitutional referendum in the worst-hit areas of Yangon and the sprawling Irrawaddy delta.

SEVERAL HUNDRED THOUSAND HOMELESS

The government 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.

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.