Myanmar state radio says the cyclone death toll has soared above 22,000 and more than 41,000 others are missing.
Up to one million people may be homeless after Cyclone Nargis and some villages have been almost totally eradicated, according to the World Food Program.
Cyclone Nargis tore through the country's heartland and largest city, Yangon, early Saturday.
Aid agencies reported their assessment teams had reached some areas of the largely isolated region. But they said getting in supplies and large numbers of aid workers would be difficult.