More than a dozen shipowners have made payments of about US$300,000 (S$406,000) apiece to release vessels seized by the Indonesian navy, which said they were anchored illegally in Indonesian waters near Singapore, according to sources with direct knowledge of the matter.

The dozen sources include shipowners, crew and maritime security sources all involved in the seizures and payments, which they say were made either in cash to naval officers or via bank transfer to intermediaries who said they represented the Indonesian navy.

The seizures and payments were first reported by Lloyd's List Intelligence, an industry website.

Rear-Admiral Arsyad Abdullah, the Indonesian naval fleet commander for the region, said in a written response to Reuters that no payments were made to the navy and that it did not employ any intermediaries in legal cases.

"It is not true that the Indonesian navy received or asked for payment to release the ships," he said.

He added that there had been an increasing number of seizures of ships in the past three months for anchoring without permission in Indonesian waters, deviating from the sailing route or stopping mid-course for an unreasonable amount of time. All the seizures were in accordance with Indonesian law, Rear-Adm Abdullah said.

The Singapore Strait, one of the busiest waterways in the world, is crowded with vessels waiting to dock at Singapore, a regional shipping hub where the Covid-19 pandemic has led to long delays.

Ships have for years anchored in waters to the east of the strait while they wait to port, believing they are in international waters and therefore not responsible for any port fees, two maritime analysts and two shipowners said.

The Indonesian navy says this area comes within its territorial waters and it intends to crack down harder on vessels anchoring there without a licence.

Around 30 ships, including tankers, bulk carriers and a pipeline-laying vessel, have been seized by the Indonesian navy in the last three months and the majority have since been released after making payments of US$250,000 to US$300,000, according to two shipowners and two maritime security sources involved.

Making these payments is less costly than potentially losing out on revenue from ships carrying valuable cargo, like oil or grain, if they are tied up for months while a case is heard in Indonesian courts, two shipowners said.

Two crew members of seized ships said armed navy sailors approached their vessels on warships, boarded them and escorted the ships to naval bases on Batam or Bintan, Indonesian islands south of Singapore, across the strait.

The ship captains and crew were often detained in cramped, sweltering rooms, sometimes for weeks, until shipowners organised cash to be delivered or a bank transfer was made to an intermediary of the navy, two detained crew members said.

Rear-Adm Abdullah said ship crew were not detained. "During the legal process, all crew of the ships were on board their ships, except for questioning at the naval base. After questioning, they were taken back to the ships," he said.

Mr Stephen Askins, a London-based maritime lawyer who has advised owners whose vessels have been seized in Indonesia, said the navy was entitled to protect the country's waters, but if a ship was seized, then some form of prosecution should follow.

"In a situation where the Indonesian navy seems to be (seizing) vessels with an intention to extort money, it is difficult to see how such a (seizure) could be lawful," he said.

Lieutenant-Colonel La Ode Muhamad Holib, a spokesman for the Indonesian navy, said some vessels seized in the last three months were released without charge due to insufficient evidence.

Five ship captains were being prosecuted and two others had been given short prison sentences and fined 100 million rupiah (S$9,500) and 25 million rupiah, respectively, he said.

REUTERS