THE captain of a fuel tanker has been jailed for 15 days and fined IDR200 million (US$13,350) for ancoring illegally, an Indonesian Navy spokesman said.

The Nord Joy, a Panama-flagged oil products tanker, was detained on May 30 while anchored in Indonesian waters to the east of the Singapore Strait, one of the world's busiest shipping lanes.

Indonesian naval officers asked for an unofficial payment of US$375,000 to release the vessel, two people involved in the negotiations told Reuters.

The Indonesian Navy denied any such payment was requested and said the vessel was being held for anchoring in its waters without a permit. Synergy Group, the manager of the Nord Joy, also said it was not aware of any request by the navy for money.

The vessel has been released after a court on July 7 handed down the jail sentence and fine to Vivek Kumar, the ship's captain, said navy spokesman Julius Widjojono.

Synergy Group confirmed its vessel had been released after a court hearing on Batam, an Indonesian island south of Singapore that is home to an Indonesian naval base.

The tanker currently anchored to the west of Singapore en route to Tanjung Pelepas port in Malaysia, according to Refinitiv ship tracking data.

Last year, Reuters reported a dozen similar detentions by the Indonesian Navy in waters to the east of Singapore. In those cases, the ship owners made unofficial payments of about $300,000 each and the vessels were released.