The United States, Amnesty International and the main opposition party sharply criticized a state of emergency declared by the government of the Maldives, expressing concern it might lead to a new crackdown on dissent.

The emergency act on Wednesday follows an explosion on the president's boat and the discoveries of a bomb and weapons. It gives the military and police powers to enter and search homes without warrants and make arrests virtually at will.

Protests, labor strikes and travel by citizens between the Indian Ocean archipelago's many islands are forbidden during the 30 days the measure will be enforced.

The Maldives has been tense since a Sept. 28 blast on the president's speedboat and a subsequent series of arrests of people, including Vice President Ahmed Adeeb, on suspicion of involvement in the explosion.

Gayoom was unhurt by the blast, which the government called an assassination attempt. The U.S. FBI, which investigated the explosion, said it found no evidence that it was caused by a bomb.

The military said Monday it found a homemade bomb in a parked vehicle close to the president's official residence. Days earlier, an arms cache was found on an island being developed as a tourist resort.

The declaration effectively thwarts plans by the main opposition Maldivian Democratic Party to hold a mass rally on Friday demanding the release of its jailed leader, former President Mohamed Nasheed.

The party called for President Yameen Abdul Gayoom's resignation, saying he has lost control of the country.

"Yameen has jailed or threatened every opposition leader, placed criminal charges against 1,700 opposition activists, and is now turning on his own by jailing the vice president. For the good of the nation, it is time for Yameen to resign," party spokesman Hamid Abdul Gaffoor said.

The United States voiced deep concern about recent events and urged the government "to restore immediately full constitutional freedoms to its citizens by terminating the state of emergency." State Department spokesman John Kirby also called for an end to politically motivated prosecutions and detentions, including that of Nasheed.

Abbas Faiz, Amnesty International's Maldives researcher, said the emergency declaration was surprising and that the government hasn't given a clear justification for its move that curtails many rights including freedom of assembly.

"The declaration of a state of emergency must not be a precursor to a further crackdown on dissent or other human rights violations," he said.

Foreign Minister Dunya Maumoon said that the measures were "pre-emptive and precautionary" and that airports, transport hubs and tourist resorts are all safe.

"The security of our resorts and islands is not under threat and we have received no evidence to suggest otherwise. The Maldives is safe for international visitors," she said in a statement.

The Parliament is expected to vote on the emergency Thursday and it is likely to be passed with Gayoom's party commanding a majority.

Best known for luxury island resorts and beaches, the Maldives has had a difficult transition to democracy since holding its first multiparty election in 2008, which ended 30 years of autocratic rule by Gayoom's half-brother.

Nasheed, the country's first democratically elected leader, resigned following public protests against his decision to order the arrest of a top judge in 2012.

In 2013, Gayoom defeated Nasheed in a disputed election in which the Supreme Court annulled the results of the first round, which Nasheed was leading, and delayed a revote until Gayoom was able to negotiate a winning coalition with other parties.

Nasheed is now serving a 13-year prison sentence under a terrorism law for his role in arresting the judge. His trial was widely criticized for its apparent lack of due process.