Plainclothes police officers in Burma are patrolling the country's largest city, Rangoon, following days of public protests against the high price of fuel.

The streets of the commercial capital were calm but tense Sunday as security officials fanned out across the city.

Burmese authorities say they have detained at least 49 people who took part in the protests over the past week.

Reports say 13 leading activists who were detained in the crackdown have been moved to Burma's notorious Insein prison, outside Rangoon. Among them is prominent pro-democracy leader Min Ko Naing. The activists could face up to 20 years in prison.

The activists have been protesting a decision by Burma's military government to double fuel prices at state-owned gas stations.

The price hike made gas and public transportation too expensive for many residents of the impoverished country.

Demonstrations are extremely rare in Burma, where security forces tolerate little dissent.

The 13 activists transferred to Insein prison were leaders of Burma's last major mass demonstrations in 1988. At that time, they led a student uprising against military rule triggered by frustration with the country's poor economy. An estimated three thousand people were killed when the army put down the protests.

Burma's government has been widely criticized for human rights violations, including the extended detention of pro-democracy opposition leader Aung San Suu Kyi and more than 1,200 other political prisoners.

Some information for this report was provided by AFP, AP and Reuters.