A small bomb at the offices of a pro-junta group in Burma has prompted the government to step up its surveillance of Buddhist monasteries and dissidents ahead of anniversaries that sometimes serve as flashpoints for dissent.

The explosion at a Union Solidarity and Development Association (USDA) office in north Rangoon on Tuesday caused only minor damage, official newspapers said, but prompted the junta to issue a call for people to watch out for “saboteurs”.

“Responsible officials are investigating the incident to expose the culprits,” the Myanma Ahlin said, urging increased public vigilance.

The USDA is a social organization founded by the Burma’s ruling generals in 1993 and now claiming 24 million members—an unlikely figure given that the entire population is only 57 million.

Increasingly, it is seen as the junta’s political party-in-waiting should it ever permit democratic elections.

USDA heavies, or gangs organized by the USDA, were used to intimidate and arrest opposition groups in August and September’s protests led by Buddhist monks against soaring fuel costs and declining living standards.

With the looming first anniversary of the protests—the biggest challenge in nearly 20 years to more than four decades of military rule—the junta’s spies have been at work for any signs of trouble in key Buddhist monasteries.

One major date is likely to be August 8, the numerically auspicious 08-08-08 and 20th anniversary of an “8-8-88″ student uprising crushed by the army with the loss of an estimated 3,000 lives. “Townships officials came to the monasteries last week to find out the situation,” one Buddhist monk from eastern Rangoon told Reuters. He did not want to be identified. “They wanted the monks to report them the arrival of overnight guests,” he said.

August 8 is also the opening day of the Olympic Games in China, the generals’ main commercial and diplomatic backer.

About 3,000 protesters, including hundreds of Buddhist monks, were arrested in last year’s crackdown, in which the United Nations estimates at least 31 people were killed.

Most of those detained have been released, although Amnesty International estimates 700 continue to be kept behind bars. Monasteries that took part in the protests were closed and thousands of monks forced to return to their towns and villages.

“The monks who were involved are still under surveillance and abbots are under pressure not to let them back in,” one monk said.