President Gayoom has been ruling the Maldives for 25 years

Government spokesman Dr Ahmed Shaheed said the emergency was declared on Friday after a rare show of dissent in the one-party nation turned violent.

Four police officers were reportedly stabbed and about 50 arrests made.

Political parties are banned in the Maldives, where President Maumoon Abdul Gayoom has ruled for 25 years.

The emergency order gives President Gayoom the power to suspend the constitution and take any steps necessary to maintain peace.

Baton charge

An indefinite curfew was imposed in the capital, Male, after police used tear gas to disperse the protesters, witnesses and officials said.

Gradually the crowd got angrier and angrier... [The protest] just took a life of its own Ibrahim Ismail, reformist politician

The BBC's Sanjeev Srivastava in Sri Lanka says protests began when a group gathered outside the national police headquarters in Male demanding the release of four reformists detained in the past week.

As more people joined the protesters after Friday prayers in this Islamic country, the authorities decided to release the reformists.

But the gesture failed to pacify the pro-democracy activists who started to demand the immediate resignation of hardline ministers in the Gayoom cabinet and the Male police commissioner.

As the crowd became more restive, the police baton-charged the protesters.

The police action sparked off a riot, with protesters stabbing four police officers and setting ablaze some government buildings.

Rights suspended

By evening, the government declared a state of emergency

MALDIVES BASICS 1,200 islands in archipelago Population is over 300,000 One-party rule since 1978 Low-lying islands vulnerable to rise in sea-levels

State radio announced certain rights of citizens had been suspended and that people were banned from demonstrating or expressing views critical of the government.

The government spokesman, Dr Shaheed, said: "We hope to lift the emergency as soon as we find out which elements were trying to subvert the political process and incite violence."

Anti-government protests demanding democratic reforms broke out in the island nation for the first time last year.

Correspondents say that the recent incident appears to be another sign of increasing frustration with the slow pace of political reform in the Maldives.

President Gayoom has suggested changes to the constitution which would limit his powers and permit political parties in the country.

Opponents of the government say it is responsible for arbitrary arrests, detention without trial and torture in prison.