But as the People's Majlis prepared to debate allowing the registration of political parties, police arrested four leading opponents of President Maumoon Abdul Gayoom, who have formed a party in exile in neighbouring Sri Lanka.

"We hope that by this afternoon the Majlis will approve the registration of parties," Chief Government spokesman Ahmed Shaheed told Reuters by telephone from the archipelago off the toe of India, famed for its luxury resorts and world class scuba.

"We hope there could be 3, or 4 or 5 parties seeking pre-registration as soon as Sunday," Shaheed added. "Police are saying they have information that (the arrested) planned to set a mob on the parliament to intimidate members of the Majlis."

Gayoom, who has ruled the Maldives since 1978 and is Asia's longest-serving ruler, promised to ease his stranglehold on power with a raft of political reforms after human rights groups harshly criticised his administration's rights record.

The present constitution of the mostly Sunni Muslim nation of nearly 300,000 people does not allow the formation and operation of political parties, and the Majlis is made up of independent candidates.

The Maldivian Democratic Party (MDP), which operates out of Sri Lanka but whose independent supporters have won parliamentary seats in key atolls, slammed Thursday's arrests, saying they proved Gayoom was insincere.

The four arrested include MDP party leader Mohamed Nasheed, who returned to the Maldives in April after 18 months of self-imposed exile.