Sunday's protest sparked the arrest of at least 13 activists

Htin Kyaw, 44, who has been detained three times this year for protesting over living standards, was beaten as he was seized on Saturday, witnesses said.

Mr Kyaw had apparently been planning another protest before his arrest.

Two rare protests were held in Burma's capital Rangoon last week. Sunday's rally was the biggest in a decade.

The authorities in Burma have been rigorously checking cars, buses and transport terminals to find those they held responsible for the demonstrations.

Another man was arrested with Mr Kyaw and both shouted anti-government slogans as they were arrested.

Open trials

Other activists who were arrested earlier this week face up to 20 years in jail, official papers revealed. Some of them are among the country's most prominent dissidents.

Many of these leading campaigners are members of the pro-democracy 88 Generation Students group which was at the forefront of a failed uprising in 1988.

Nyan Win, spokesman for the National League for Democracy (NLD), said: "They have made the strongest possible allegations against these activists.

"Their trials must be open. These activists should be heard in open court."

Last week's fuel price rises left many people struggling to find the money to travel to work.

Other arrested activists include Min Ko Naing and Ko Ko Gyi - some of Burma's most well-known dissidents after Nobel Peace Prize laureate Aung San Suu Kyi.

The NLD's leader, 62-year-old Ms Suu Kyi, has spent most of the past 17 years under house arrest.

The NLD won landmark elections in 1990 but the junta never recognised the result.