TEHRAN, Young Journalists Club (YJC) - "Our divers found all the bodies of the missing 12 crew members inside the ship," a coastguard official told AFP.
Thursday's collision occurred 400 kilometers north of the Oki Islands in the Sea of Japan, also known as the East Sea.
The Chinese vessel, the 290-ton "Lurong Yuanyu 378," had 16 crew members in total. Four had already been rescued.
The Hong Kong-flagged ship was identified as "Brightoil Lucky", a 63,294-ton tanker carrying 21 crew members.
The tanker's crew were believed to be safe.
Japan had deployed three patrol boats to search for the missing crew, after responding to a plea for help from their Chinese counterparts.