Thailand's foreign minister said after a meeting with Myanmar's ambassador in Bangkok that the losses from Cyclone Nargis have been "much greater" than previously thought.
The death toll is likely to rise further as rescue workers struggle to reach remote settlements, while the nationwide number of displaced people could reach millions. Some 40,000 people are currently listed as missing.
Nyan Win, Myanmar's foreign minister, said on state television that 10,000 people had died in just one town, Bogalay, to the south of Yangon, when four-meter (12 foot) tidal waves and raging winds swept away shabby houses in low-lying rural areas.
A state of emergency has been introduced in the five worst-hit districts - the Irrawaddy delta, the cities of Yangon and Pegu, and the states of Karen and Mon. Most of the deaths came in the low-lying Irrawaddy delta region.
The foreign minister said his country would welcome international aid efforts.
Russia's outgoing president Vladimir Putin expressed his condolences in a telegram and said his country was ready to provide all the necessary aid to the disaster-hit country.
"Russia is ready to provide all the necessary assistance to eradicate the consequences of this natural disaster," - the president said.
The European Union has allocated 2 million euros ($3 million) in initial emergency aid to provide thousands of now-homeless people with tents and fresh water.
"This is a terrible catastrophe that demands a quick and effective humanitarian response," EU Humanitarian Aid Commissioner Louis Michel said in a statement.
The cyclone has also forced the country's authorities to postpone until May 24 a referendum on a military-backed constitution, but only in the worst-hit regions. Residents of other areas will go to the polls as scheduled on May 10.
Myanmar's ruling junta seized power in 1988, and although a general election was subsequently held in 1990, the military authorities refused to honor the results when pro-democracy leader Aung San Suu Kyi's National League for Democracy Party won. The referendum is supposed to eventually lead to a general election in 2010.
