JAKARTA • The Indonesian navy has detained a boat captained by a Singaporean for allegedly fishing in Indonesian waters without permission.

The boat was intercepted around 7.30pm on Sunday around the waters of Tanjung Berakit, Bintan island, according to detik.com news website.

The boat had a crew of four, including the Singaporean and three Indonesians, Commodore S. Irawan, navy commander in Tanjung Pinang, told The Straits Times.

There were also 13 passengers on board - six Singaporeans and seven Malaysians.

They were being held at the Tanjung Pinang naval base's detention centre on Bintan.

The crew will be prosecuted because they were caught fishing without permit in Indonesian waters, Mr Irawan said.

"During the interrogation, they gave inconsistent information. First, they said they were just passing by and were pushed by tides towards Indonesian waters. Then, they said they were out for fishing," he said.

The detik.com report said the boat was an Indonesian boat.

The website named the Singaporean captain as Mr Shoo Chian Huat, quoting a navy spokesman.

"All the passengers will be deported, but we have not decided the timing. The crew will be prosecuted using fishery law. We may sink the boat; we will report this incident to our superiors. We are treating all of them properly."

The commander added that the boat is being inspected and investigators are also looking into the possibility that it is linked to illicit drug trade. The boat's detention followed tough policies, adopted by Indonesia in the last two years to curb poaching in its vast waters, that it said have helped double the catch of some legal fishermen.

Since 2014, Indonesia has sunk some 170 vessels caught poaching in Indonesian waters and impounded 700 others. Most of the sunk ships were from Vietnam and the Philippines. Last year, two Singapore-registered ships were detained when they entered Indonesian waters in the Strait of Malacca and near Batam.