The Japanese Defense Ministry said Saturday that five Chinese and five Russian warships had sailed through the Soya Strait between Hokkaido and Sakhalin 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."

The Chinese and Russian vessels -- destroyers, frigates and supply ships -- were located about 200 kilometers southwest of Rebun Island in Hokkaido around 3 p.m. Friday and had moved eastward through the strait by Saturday, according to the ministry.

Undated photo shows a Chinese navy guided missile destroyer sailing through the Soya Strait. (Photo courtesy of the Japanese Defense Ministry's Joint Staff)(Kyodo)

Undated photo shows a Russian navy frigate sailing through the Soya Strait. (Photo courtesy of the Japanese Defense Ministry's Joint Staff)(Kyodo)