SINGAPORE - The port authority of Singapore has confirmed that two of four vessels detained in Indonesia in separate incidents over the last two weeks are Singapore-registered.

Earlier reports had suggested all four are Singapore-registered.

In a statement on Friday following media queries, the Maritime and Port Authority of Singapore (MPA) also said it is also incorrect that four Singaporeans were detained.

In fact, only one is a Singaporean marine surveyor who has since been released.

None of the other crew members on board the four vessels were Singaporeans.

In the first incident reported on March 5, 'DM 55' is a Singapore-registered vessel while 'Sea Sparrow 1' is Belize-registered.

In the second incident first reported on March 9, 'ASL Glory' is a Singapore-registered vessel while 'AST 1837' is Indonesia-registered.

MPA is in contact with the Indonesian authorities to assist in the investigation of the incidents.

"We have also advised the shipping community that all vessels should follow international best practices and adhere to the relevant coastal state laws" the port authority said.

The vessels were detained for allegedly not having required permits.