Three sailors were missing after a Vietnamese ship carrying crude oil exploded and sank off the country's southern coast on Wednesday, a rescue official said.
Ships were mobilised to search for the missing crewmen, said Luong Truong Phi, deputy head of the search and rescue centre in Vung Tau city.
Twelve other sailors were rescued in good condition, Phi said, adding the cause of the blast was unknown.
"We have to wait until we can bring up the vessel, to understand why the explosion occurred," Phi said.
State-linked VNExpress news website said the ship, the Nhat Thuan, was carrying 1,793 cubic metres (2,331 cubic yards) or about 11,300 barrels of crude and 10,000 litres (2,600 gallons) of diesel to an offshore tanker when the incident occurred.