The death toll from Burma's devastating cyclone has now risen to more than 22,000, state media have said.

Some 41,000 people were also missing, three days after Cyclone Nargis hit the country, according to state radio.

The report came as aid agencies begin what they expect to be a big operation to help hundreds of thousands said to be without clean water and shelter.

Meanwhile, criticism is mounting over the handling of the crisis by Burma's military leaders.

A number of Burmese nationals and some foreigners say they have not been properly warned by the junta about the approaching storm.

Some eyewitnesses have also said the government's response to the disaster was slow and inadequate.

Meanwhile, Burma's opposition National League for Democracy (NLD), led by detained Nobel laureate Aung San Suu Kyi, has criticised the junta for pressing ahead with a constitutional referendum - just a week after the devastating cyclone, Reuters reported.

State media reported on Tuesday that 22,464 people had now been confirmed as dead.

Earlier, Burmese officials said that up to 15,000 people had died.

More deaths were caused by the tidal wave than the cyclone itself, Minister for Relief and Resettlement Maung Maung Swe told reporters in Rangoon.

"The wave was up to 12ft (3.5m) high and it swept away and inundated half the houses in low-lying villages," he said. "They did not have anywhere to flee."

Some 95% of the homes in the city of Bogalay in the Irrawaddy river delta were destroyed, he added.

Burma's military leaders have said they will accept external help, in a move that correspondents say could reflect the scale of the disaster.

State TV said on Tuesday that the government had decided to postpone to 24 May the referendum on a new constitution in areas worst-hit by the cyclone - including the former capital Rangoon and the Irrawaddy Delta.

But it said that the vote initially planned for 10 May would proceed as planned in the rest of the country.