The 31 ethnic Indians, against whom attempted murder charges have been dropped, would be charged with taking part in an illegal assembly and not for being followers of the non-governmental Hindu Rights Action Force, Malaysia's top legal official has said.

"The charge is in accordance with the law. All 31 individuals involved had written to me deploring Hindraf and claimed that they were not Hindraf members. They promised not to take part in any future illegal assembly," Attorney-General Gani Patail said.

"The decision to withdraw the charges (for attempted murder of a police officer) was also fair as we could not ascertain who had thrown a stone that hit the victim," he was quoted by state-run Bernama news agency as saying.

The court acquitted 31 people charged with attempting to murder a police officer during a massive November 25 rally organised by Hindraf in front of the Sri Subramaniar temple in Batu Caves near in Kuala Lumpur to protest the alleged marginalisation of ethnic Indians in the country.

The government had declared the rally as illegal.

Judge Nursinah Adzmi made the decision after allowing the application by the Attorney-General to withdraw the charges against them.

Twenty-five people among the group of 31 face other charges, including those relating to causing damage to seven cars and two gates of the Sri Subramaniar temple.

Meanwhile, the cyber crimes division of Malaysian police is keeping an eye on the supporters of Hindraf and their activities, the country's Deputy Internal Security Minister has said.

Malaysians need not feel intimidated if their actions were within the confines of the country's law, the Minister, Fu Ah Kiow, said.

"The action by Hindraf leaders and their seditious remarks and allegations must be stopped to prevent the situation from getting out of hand," the minister said, commenting on the detention of the five Hindraf leaders under the Internal Security Act, which permits detaining a person for two years without trial.

Fu said the detention order was enforced as a last resort as police intelligence revealed that Hindraf had made attempts to contact militant groups overseas.

He said that due to their actions, the government was forced to invoke the ISA.

"We hope there will not be another round of detention," he said, adding that the government would not have invoked the ISA if peace, security and harmony of the people were not at risk.