Maldives President Abdulla Yameen has declared a 30-day state of emergency ahead of a planned anti-government rally.
The president’s declaration gives security forces sweeping powers to arrest suspects.
The move comes two days before the planned protest by the country’s main opposition, the Maldivian Democratic Party (MDP).
MDP leader Mohamed Nasheed was jailed in March after a widely criticized conviction under anti-terror laws.
Attorney-General Mohamed Anil said a cache of firearms and explosives had recently been discovered, as well as plots to use dangerous weapons.
On November 2, authorities said they had defused a bomb planted near the presidential palace.
“The military and police found weapons and an explosive from two locations,” Muaz Anil said.
“Because these would be a threat to the public and the nation, the National Security Council has advised to take immediate steps to protect the people of Maldives,” he added.
The Maldives has been rocked by political infighting in recent weeks, with Vice-President Ahmed Adeeb arrested in connection with an alleged plot to assassinate the president by blowing up his boat.
Abdulla Yameen narrowly escaped injury but his wife was hurt when a blast struck the boat, which he was using to return home from the airport last month.
Ahmed Adeeb has been charged with treason.
The FBI in the US investigated the blast and said it found no evidence that it was caused by a bomb.