Kuala Lumpur - A Malaysian minister resigned Monday following his outspoken criticism of the government's use of a draconian security law to stifle political opposition.

In a rare show of defiance against Prime Minister Abdullah Ahmad Badawi, Zaid Ibrahim, minister responsible for legal matters, stepped down as an act of protest, sources were quoted as saying by the Malaysia Star newspaper.

Zaid was unavailable for comment.

On Friday, the government detained three people - an opposition lawmaker, a journalist and an anti-government internet blogger - under the Internal Security Act which allows indefinite detention without trial.

The journalist was subsequently freed Saturday, but the Teresa Kok of the opposition Democratic Action Party and blogger Raja Petra Kamarudin remain in custody.

The security act was originally drafted decades ago to fight a communist insurgency.

Zaid criticized the use of the law against civilians and said he was prepared to resign over the issue.

"It is time for the government to go back to the original spirit of the ISA and it should only be used on armed terrorists or those out to topple the government by force," he had said Sunday.

"I joined his administration to make changes and everybody knows, I am also for a more open-form of press reporting," he was quoted as saying by the newspaper.

Zaid's resignation added another crack to Abdullah's ruling party, which is facing a crisis with members calling for the party leader's resignation.

Abdullah is also threatened by opposition leader Anwar Ibrahim who pledged to oust the government by convincing sitting legislators of the ruling alliance to change their party allegiance.

Anwar's opposition alliance held a mass rally late Monday in a suburb outside Kuala Lumpur to protest the government crackdown, which he said was aimed at foiling his plans to take power.

Anwar needs 30 defections to secure a parliamentary majority to topple Abdullah's National Front coalition, which has been in power since independence in 1957. (dpa)