They had stormed the vessel and siphoned off some of its gas oil cargo, a crew member claimed on Thursday.
The deputy captain of the 2012-built, 5,929 dwt products tanker ‘Sunrise 689’, Pham Van Hoang, talking to local newswires, said a group of more than 10 men, who he thought were Indonesian, armed with guns and knives boarded the tanker from two speedboats shortly after it left Singapore for Vietnam on 2nd October.
He said that the pirates destroyed the communication and navigation systems and put all 18 Vietnamese crew members into a room. The pirates then siphoned off some of the gas oil into their vessels.
One crew member reportedly broke his leg when he fell trying to flee from the pirates.
Hoang said the crew was freed early on Thursday and that the tanker was about 90 miles off Vietnam's southern tip.
The vessel, which was transporting more than 5,000 tons of gas oil from Singapore, should have arrived at a port in the central province of Quang Tri on Wednesday.
The ‘Sunrise 689’was the 12th such piracy case since April in Southeast Asia, where tankers have been hijacked and then released after the cargoes were stolen, according to the International Maritime Bureau.