Yangon - In a rare show of defiance, a bomb was detonated Tuesday at an office of the pro-government Union Solidarity and Development Association (USDA), witnesses and security personnel said.

The explosion, which occurred at 6:30 am (1200 GMT) at the USDA's Shwe Pyi Tha office, in Yangon, destroyed some tables but caused no casualties.

The USDA, which boasts millions of members, is expected to be transformed into a proxy political party for the military to contest a general election scheduled in 2010.

Acts of violence against the USDA are rare in Myanmar, which has been under military rule since 1962.

Growing frustration with the junta's rule flared up in September, last year, when tens-of-thousands of Burmese took to the streets of Yangon to protest the country's worsening economic plight and lack of democratic progress.

The army brutally cracked down on the monk-led demonstrations, killing at least 31 people and leaving dozens missing.

The regime's callous handling of relief efforts for victims of Cyclone Nargis, which hit Myanmar's central coast on May 2-3 leaving up to 139,000 dead or missing, has added to the discontent, sources said. (dpa)