Vietnamese authorities have arrested 11 suspected pirates aboard a chemical tanker after the first hijacking of a vessel en route to Malaysia's Borneo island in years, the International Maritime Bureau said Friday.
Pirate attacks off Malaysia have dropped in recent years, following stepped-up patrols and co-operation with neighbouring countries to secure the region's waterways.
"IMB hopes that the authorities will take action and investigate the incident to contain and stop this type of menace," said Noel Choong, head of the bureau's Kuala Lumpur-based piracy reporting centre, adding it was a "serious" concern.
The Malaysian-owned vessel lost communication on Saturday after leaving the country's southern Johor state, Choong said.
The vessel was likely attacked in the South China Sea, he said, adding that the IMB, which sent out an alert to help locate the tanker, was still waiting for further details.
Vietnamese marine authorities managed to intercept the tanker on Thursday, arresting 11 suspects. The pirates had changed the ship's name and were flying a Honduran flag.
The tanker's nine crew members were released at sea on Wednesday by the pirates, said Choong, adding the crew were all safe after being rescued by local fishermen.
Vietnam's Tuoi Tre News reported the sailors, five from Myanmar and four from Indonesia, had been forced onto a life raft.
It said the suspected pirates were all Indonesians and had been masked, according to initial testimonies, and that Vietnamese authorities opened fire on the vessel before making the arrests.
Vietnamese authorities could not immediately comment on the case when contacted, while the Malaysian owner of the vessel, named Zafirah, could not be reached.
The maritime bureau praised Vietnamese and Malaysian authorities for their efforts.
"Ships sailing in the region should maintain anti-piracy watches especially at night in Asian waters," Choong said.
In October, four Indonesian suspected pirates were arrested for trying to hijack a tugboat and barge off Malaysia's Sarawak state. Choong said authorities were still investigating that case.
The United Nations this week called for stronger prosecutions of pirates and more action by shipping companies to deter bandits at sea.
The body's deputy secretary general said while attacks this year had been reduced off the coast of Somalia, a piracy hot spot, numbers could take off again unless countries take action.
According to International Maritime Organization (IMO) figures, there were 291 attacks against ships in the first 10 months of the year and 293 crew still being held hostage.
East Africa, West Africa and Asia-Pacific are the worst hit zones.