The move comes after a leading human rights activist was questioned on Feb 12 for allegedly violating the strict rules about holding public meetings.

"It is one thing to have a group of people gather to hear a person or persons speak, but quite another when people come together for a specific cause," said a police statement.

Chanting slogans, displaying placards and "gesticulations" such as "clenching of fists" were "indicative of a demonstration or of disorderly behaviour," the statement said.

The statement came on Feb 12 ahead of a court's rejection Feb 13 of an appeal by Singapore's leading opposition politician to throw out seven defamation suits brought against him by top government officials, including elder statesman Lee Kuan Yew. Joshua "J. B." Jeyaretnam, the 74-year-old leader of the Workers' Party, said he had asked the court to dismiss the cases when the plaintiffs insisted on reopening them after three years. He said he believed the government was "opening fire" now because "elections are going to be held this year".

Human rights groups say the government regularly sues opponents for defamation as a way of silencing dissent. Mr Jeyaretnam is the target of a separate legal action seeking to declare him bankrupt because he allegedly failed to pay an instalment from another libel suit - an action that could strip him of his parliamentary seat, one of only three held by the opposition.

"He was unable to satisfy the court that he had any legal merit and [the motion to throw out the suits] failed. That's really the bottom line," said Mr Lee's lawyer Hri Kumar, referring to the Feb 13 court action.

The opening of Speakers' Corner last September was widely thought to be a sign of liberalisation in the city-state known for its strict social controls.

While some opposition figures have boycotted the corner - calling it no substitute for true freedom of expression - a number of Singaporeans have used it to speak on everything from press freedoms to the cost of medicine.

James Gomez, a leading civil rights activist, was ordered to appear before police both on Saturday and Monday to answer questions about his involvement in two events promoting civil liberties in Singapore, including one at Speakers' Corner in which participants chanted slogans against a law that permits detention without trial.

The government has said it would gradually like to grant greater freedoms to citizens, but critics say the pace of liberalisation is excruciatingly slow.