The Red Cross estimated that the cyclone death toll in Myanmar could be as high as 128,000 -- a much higher figure than a tally by the government, which continued to issue few visas to foreign aid experts, and all but shut them out of the hardest-hit area.

The grim forecast came on Wednesday as heavy rains drenched the devastated Irrawaddy River delta, disrupting aid operations already struggling to reach up to 2.5 million people in urgent need of food, water and shelter.

"Another couple of days exposed to those conditions can only lead to worsening health conditions and compound the stress people are living in," said Shantha Bloemen, a spokeswoman for UNICEF.

Myanmar's government issued a revised casualty toll on Wednesday night, saying 38,491 were known dead and 27,838 were missing.