Polls in Burma have opened for a controversial constitutional referendum, just a week after the country was struck by a major cyclone.

The devastating storm prompted Burma's military government to postpone the vote in the worst-affected districts, but it is going ahead Saturday as scheduled elsewhere.

Voting in Rangoon and four other districts - where nearly half of Burma's 53 million people live - will wait until May 24.

Burmese living abroad began casting absentee ballots last month at local embassies, which have also been sites of protests by opposition groups.

On Friday, Burmese activists rallied outside embassies in the Philippines and Thailand urging the government to call off today's referendum to focus on getting aid to cyclone victims.

International leaders, including United Nations Secretary-General Ban Ki-moon, have made similar appeals.

Burma's opposition National League for Democracy says the charter, if approved, will only strengthen the military's control over the country. The party has urged voters to cast a "no" ballot on the referendum.

But Burmese state-run media ran messages Friday reminding citizens it is their patriotic duty to approve the new charter, even as hundreds of thousands of cyclone victims desperately await aid.

Burma's military leaders say the constitution is part of a so-called "road map to democracy" that will lead to general elections in 2010.

A military government has ruled Burma since 1962. The opposition party won the last general elections in 1990. But military leaders never recognized the results of that race and instead put opposition leader Aung San Suu Kyi under house arrest.

Some information for this report was provided by AFP,.