TOKYO, March 17. /TASS/. Japan’s government has made representations to the Russian side following the recent passage of four Russian assault ships through the Sangar Strait (Tsugaru Strait) between the Japanese Islands of Honshu and Hokkaido, Japan’s Chief Cabinet Secretary Hirokazu Matsuno said on Thursday.

"As for the increased activities of the Russian fleet near our country, including the passage of four ships, it causes serious concern and we are keeping a close eye on such actions. We have already made representations to the Russian side demanding it refuse from actions augmenting tensions in this region," he said.

Japan’s Self-Defense Forces Joint Staff said on Wednesday that four assault ships of the Russian Navy passed through the Sangar Strait between the Islands of Honshu and Hokkaido. According to released photos, one of the ships was carrying more than ten trucks.