SEOUL (REUTERS) - A Mongolian-flagged cargo ship has sunk off the southern coast of South Korea, with most of the 16 North Korean crew members on board missing, South Korean coast guard officials said on Friday.

Two crew members were found dead and three were rescued, while a search was under way for the other 11 crew still missing, the officials said.

The Grand Fortune 1 was sailing from the Chongjin region on North Korea's east coast for a Chinese port carrying iron ore, said one official, who requested anonymity because he was not authorised to speak to the media.

The vessel sails regularly between North Korea and China, according to Reuters' ship tracking system.

The rescued crew members were taken to a South Korean hospital for treatment, according to the coast guard.