Dozens were hospitalised Friday when police fired teargas and used sticks and batons to disperse hundreds of protesters demanding the release of political prisoners in the tourism-dependent Indian Ocean archipelago, witnesses said.
Local officials on Saturday said at least 80 people were rounded up in the protest outside the National Security Service (NSS) headquarters in the 1.6-kilometer (one-mile) long capital island Male.
Gayoom's office said police tried to "restrain" the crowds for 17 hours but that protesters torched a government building and stabbed two unarmed policemen.
"Having exercised maximum restraint despite criminal acts, when the mob attempted to charge down the entrance to the police headquarters, the authorities had no alternative but to implement measures to disperse the mob," Gayoom's office said in a statement.
It said the emergency, which gives sweeping powers to security forces to detain suspects, will be in force in Male and neighbouring islands until further notice.
Gayoom had earlier clamped a curfew in the capital following the clashes.
The dissident Maldivian Democratic Party, which is based in neighbouring Sri Lanka and not recognised by Gayoom's administration, said NSS men went to the homes of party supporters and beat them up.
"Activists were beaten up in their homes and were also subject to verbal abuse and threats by the NSS," a party statement said.
The party, which favours multi-party democracy in the nation of 270,000 Sunni Muslims, called for the international community to take action to prevent the country from slipping into chaos.
Regional power India voiced concern about the situation in Maldives.
"We are naturally concerned. We are watching the developments," Indian foreign ministry spokesman Navtej Sarna said in New Delhi.
Human rights group Amnesty International urged Maldives to adhere to global standards in treating detainees.
"Amnesty International is calling on the Maldivian government to ensure their safety and security, after emerging reports of security forces beating those in detention," the human rights watchdog said in a statement.
The London-based group said it was "deeply concerned" at reports of large numbers of injured people needing hospital treatment after the police used sticks and batons to attack them during the demonstrations.
Gayoom has ruled the Maldives since 1978, turning the once fishing-based nation of 1,192 coral islands into a prosperous upscale tourist destination.
But he has faced increasing criticism both within Maldives and from the United States and Europe for his failure to tolerate an opposition.
Gayoom began cautious reforms after an unprecedented riot in Male last September triggered by the death of an inmate at a nearby prison.
Last month, legislators staged an unprecedented walkout over disagreements on electing a speaker to spearhead the democratic reforms.
The special assembly of 108 members was elected in June to draw up a new constitution in line with the promised reforms.
Dissidents have been sceptical of the reforms, noting that the proposed new post of prime minister would be selected on the advice of parliament which is dominated by Gayoom allies.
Gayoom won a sixth five-year term as president in a yes-or-no referendum in October in which he won more than 90 percent of the vote.
