A Mongolian-flagged cargo ship with 16 North Korean crew members has sunk off the southern coast of South Korea, a South Korean coast guard official said on Friday. Three crew have been rescued and a search for the 13 crew members still missing is ongoing, the official said. The ship was sailing from the Chongjin region on North Korea’s east coast and was headed for a Chinese port carrying iron ore, the official said, requesting anonymity as he was not authorised to speak to media.