The Defense Ministry said Saturday that five Chinese and five Russian warships had sailed through the Soya Strait between Hokkaido and Sakhalin island to the Sea of Okhotsk, possibly in connection with a joint patrol in the Pacific Ocean.
Nine of the naval vessels were involved in a joint exercise in the Sea of Japan between July 18 and 23, the ministry said, adding it is carefully monitoring their movements.
Last year, Chinese and Russian warships circumnavigated Japan, prompting Tokyo to criticize the "show of force."