The Japan Coast Guard were searching for six missing Japanese crew on Friday after two cargo ships collided off Tokyo, news reports said.
The Japanese-flagged Eifuku Maru No 18, 498 tonnes, and the 2,962-tonne Jia Hui, registered in Sierra Leone, collided around 1:25 am (1625 GMT Thursday) near Izu Oshima island, 100 km south of Tokyo, the Kyodo News agency reported, citing the coast guard.
The Japanese vessel was found capsized with all its crew missing.
It was heading for Chiba, east of Tokyo, from Nagoya, central Japan.
The 13 crew of the Sierra Leone freighter, of Chinese and Myanmar nationality, were rescued from waters nearby, apparently unhurt, Kyodo said.
The ship was on its way to Busan, South Korea, from Kawasaki, south of Tokyo.