COLOMBO (REUTERS) - An explosion on a speedboat carrying Maldives President Abdulla Yameen was an assassination attempt, the minister at his office told Reuters on Tuesday, citing the findings of international investigators.

Two military officials have been arrested over the incident, Mohamed Hussain Shareef said.

Yameen was unhurt in the Sept 28 blast on board the presidential launch as it approached the capital Male, but his wife and two aides were injured.

Initially, the government said it could be due to mechanical failure.

Shareef said that theory had been ruled out by investigators from the US FBI, Saudi Arabia, Australia, and Sri Lanka.

"They are now telling me that they have enough evidence to believe that it is likely to have been an attempt on the President's life," he said by telephone from Male.

"Authorities have arrested two people... in line of command who had access to the vessel."

Yameen, 59, took power after a bitterly contested presidential election in 2013.

The leader he defeated, Mohamed Nasheed, was jailed this year after a rapid trial on terrorism changes in a case that has drawn international criticism.

A team of international human right lawyers are pressing for travel bans and targeted sanctions against top Maldivian officials.

The foreign ministry on Tuesday said "the wholly inappropriate" sanctions threat appeared to have been widened to include a suggested tourism boycott.

A broader crackdown against political dissent belies the popular image of the Maldives, an island chain with a population of 400,000, as a holiday paradise, with radicalised youths enlisting in significant numbers to fight for Islamic State militants in the Middle East.

Local investigations into the explosion on the Maldives National Defence Force launch are continuing, and security for Yameen has been beefed up, Shareef added.