Thailand's foreign minister, Noppadol Pattama, said after a meeting with Myanmar's ambassador in Bangkok, that the losses from the cyclone have been "much greater" than previously thought.
The death toll is likely to rise further as rescuers reach remote settlements, while the nationwide number of displaced people could reach millions.
The deadly cyclone with winds raging at the speed of 190 kmph (120 mph) hammered the country's former capital and largest city of Yangon, cutting off electricity and water supplies, as well as most of the telephone, internet and cell services.
Nyan Win, the Burmese 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 wings swept away shabby houses in low-lying rural areas.
The state of emergency has been introduced in five worst-hit districts - the cities of Yangon and Pegu, the Karen and Mon states and the Irrawaddy delta.
The foreign minister said his country would welcome international aid efforts.
The European Commission has allocated 2 million euros ($3 million) in initial emergency aid to provide the victims 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.
Among other contributors are Canada ($2 million), China ($1 million), the U.S. embassy in Myanmar ($250,000), and the Czech Republic ($155,000).
The cyclone forced the country's authorities to postpone until May 24 the 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.
