KUALA LUMPUR — Heavily-armed pirates have boarded a Singapore-managed tanker in the Strait of Malacca, kidnapping three Indonesian crew and stealing some of its cargo of diesel fuel, the International Maritime Bureau said Wednesday. The attack occurred early Tuesday off Malaysia's west coast, said Noel Choong, head of the IMB's Kuala Lumpur-based Piracy Reporting Centre. The tanker was believed en route to Myanmar.

"A tanker was boarded by about 12 heavily armed pirates," a report from the IMB said. It added that the pirates brought in other tankers that pumped out some of the vessel's diesel and kidnapped three crew members. "IMB is concerned about the kidnapping of the three senior Indonesian crew members," Choong told AFP, adding that the ship was now berthed off Port Klang in Malaysia for investigations.

Malaysian media said the crew only realised they had been hijacked when they saw about five or six men armed with a pistol and a machete aboard the ship. The crew comprised Indonesian, Thai, Myanmar and Indian nationals. No further details on the vessel were provided. Marine police gave the name of the ship as the Naniwa Maru 1, whose owner is from Saint Kitts and Nevis but which is Singapore-operated.

In previous attacks in the region in recent years, pirates had mostly stolen cargo but not kidnapped any crew members, Choong said. The Strait of Malacca is a key maritime highway linking Europe and the Middle East to Asia, and has long been a hunting ground for pirates. Attacks in the strait had dropped in recent years following stepped-up patrols and cooperation between neighbouring countries to secure waterways.