In a major crackdown, Malaysian authorities on Tuesday detained at least 20 opposition activists when they tried to stage a protest in front of the Parliament in Kuala Lumpur against the extension of the tenure of the Election Commission chief, hours after a prominent ethnic Indian leader was re-arrested on sedition charges.

Opposition protesters wanted to demonstrate against the amendment to a law extending the tenure of a "biased" Election Commission chief. Notwithstanding the protest, the Parliament approved the amendment.

Police blocked all roads to Parliament as activists headed to assemble there, resulting in traffic disruption across Kuala Lumpur.

Backed by trucks mounted with water cannons, police detained 12 activists heading towards Parliament, said police officer Ahmad Sofian Yassin. At least eight other opposition workers were detained later in the area, activists said.

Sixteen opposition legislators staged a walkout in Parliament to protest the arrests.

Meanwhile, police re-arrested non-governmental Hindu Rights Action Force leader P Uttayakumar after he posted bail on a sedition charge on Tuesday.

Uttayakumar, legal adviser of Hindraf, was first charged in the sessions court with posting a seditious letter on the group's website.

The lawyer pleaded not guilty before Judge Sabariah Othman, who fixed a trial date for next month. The lawyer posted a bail of 50,000 ringgit (Rs 5.9 lakh) with one surety. The judge also ordered that Uttayakumar's passport be impounded.

However, Uttayakumar was re-arrested at the entrance of the court house and taken to the Cheras police headquarters for investigation into a similar offence, national news agency Bernama said.

The letter, which Uttayakumar is alleged to have posted on the website, was addressed to British Premier Gordon Brown.

The charge under the Sedition Act carries a fine not exceeding 5,000 ringgit (Rs 59,000) or a jail term not exceeding three years or both for a first offence. The penalty for a subsequent offence is up to five years' jail.

In another development, former deputy premier and opposition leader Anwar Ibrahim was briefly detained after he returned from a foreign trip.

"The winds of democracy in Malaysia will prevail as more and more will take to the streets to remove this corrupt party from power," Anwar said in a statement.

The Malaysian capital is witnessing attempts by groups to hold demonstrations, which are rare in the Muslim-dominated country.

The first major demonstration was held on November 10 by Bersih, a group of opposition parties, when at least 30,000 people assembled and demanded electoral reforms.

On November 25, ethnic Indians numbering in thousands gathered in front of the iconic Petronas towers in the heart of the city and protested against the alleged marginalisation of the community.

On Sunday, some lawyers tried to hold a march and four of them were arrested. All demonstrations have been declared illegal by the government.