The Japanese government announced that 10 naval ships sailed through the strait that separates Japan's mainland from its northern island, Hokkaido. The vessels reportedly belonged to Russia and China, which were closely monitored by Tokyo. 

Deputy Chief Cabinet Secretary, Yoshihiko Isozaki, said in a news conference that "The government is closely watching Chinese and Russian naval vessels’ activities around Japan like this one with high interest." 

While the Japanese Defense Ministry declared that no international laws were violated in the process, the Sea of Japan saw military drills and exercises with Russia and China between October 14 to 17. 

What is most interesting about this event is that not only is this the first time that Japan confirms that Russian and Chinese vessels are sailing in its waters, but also that the Strait of Tsugaru is considered international waters in which Japan suffers territorial tensions with both countries.