Food and water are running short in the area of Myanmar hit by cyclone Nargis, and U.N. officials called the situation there "increasingly horrendous."

"There is a very real risk of disease outbreaks as long as this continues," "There is a very real risk of disease outbreaks as long as this continues," Villarosa told the media.

"Most urgent need is food and water," said Andrew Kirkwood, head of Save the Children in Yangon. "Many people are getting sick. The whole place is under salt water and there is nothing to drink. They can't use tablets to purify salt water," he said.

Hungry crowds stormed the few shops that opened in the country's stricken Irrawaddy delta, sparking fist fights, according to Paul Risley, a spokesman for the U.N. World Food Program in neighboring Thailand.

CNN's Dan Rivers, the first Western journalist into the devastated town of Bogalay, said Wednesday that the level of destruction was hard to describe.

"Ninety percent of the houses have been flattened. ... The help that these people are getting seems to be pretty much nonexistent, from what we've seen."

He saw members of Myanmar's army clearing roads but handing out little food or medicine. Local aid workers started distributing water purification tablets, mosquito nets, plastic sheeting and basic medical supplies.

State media in Myanmar, also known as Burma, reported that nearly 23,000 people died when Cyclone Nargis blasted the country's western coast on Saturday and more than 42,000 others were missing.

U.N. humanitarian chief John Holmes said Thursday that the cyclone's death toll may rise "very significantly," possibly up to 100,000 people.