Malaysia invoked a tough internal security law on Thursday to indefinitely detain five ethnic Indian activists from a group that had staged a mass anti-government protest last month.

The deputy internal security minister said the five, from the Hindu Rights Action Force (Hindraf), had been detained for up to two years because their actions threatened national security.

Last month, Hindraf stunned the government by bringing over 10,000 ethnic Indians onto the streets of the capital to complain of racial discrimination.

“They can be held for two years for sedition and also for carrying out activities that threaten national security,” Deputy Internal Security Minister Johari Baharom was quoted as saying by state news agency Bernama. One of those detained was a Hindraf leader, lawyer P Uthayakumar, who had already been charged with sedition for alleging that Malaysia practised “ethnic cleansing” of Indians, who make up about 7 percent of the population.

“They said they were arresting him under the ISA (Internal Security Act), but they didn’t say where they were taking him,” said a woman called Shantha, who answered Uthayakumar’s mobile phone after news of the detention and said she was his secretary. The Hindraf Web site named the other detainees as M Manoharan, R Kengadharan, B Ganabathi Rao and Vasanthan.

“We appeal to all our supporters to remain calm and do not listen to any rumours or untruth that may be spread to break our unity,” said a statement on the Web site. We call upon all supporters to organise nationwide prayers in temples, houses, etc. for the speedy release of our leaders.”

Prime Minister Abdullah Ahmad Badawi, who came to power four years ago promising more transparent government, had said earlier this week he would have no trouble signing a detention order to ensure public security and national stability.

The five were charged under Section 8 (1) of the ISA, which provides for a two-year detention, police said. The detention can be extended further at the minister's discretion and cannot be challenged in court.

Malaysian rights group Suaram said 84 people were currently being held under the ISA. One man was detained for 17 years before he was released. The Hindraf rally was one of two mass protests last month. A  crowd of around 10,000 people had earlier turned out on the streets of the capital to demand fairer elections, amid expectations of a snap poll by March 2008.

But the Indian rally  aroused deep concerns within government because of the country’s history of tense and sometimes explosively violent race relations.