Twelve other mariners were rescued by fishermen after the Van Don-2 sank early Tuesday about 400 kilometres off the coast of Ba Ria-Vung Tau, said Bui Ngoc Tri, of the southern province's search and rescue centre.

"Our search is hampered by bad weather," he added.

The ship, weighing 6,900 deadweight tonnes, was transporting material for making iron from Malaysia to Ho Chi Minh City, Tri said. It belongs to the Quang Ninh Sea Transport company based in northern Quang Ninh province.