Foreign Minister Fumio Kishida on Friday expressed concern about "escalating" moves by Chinese navy ships following repeated entries into or near Japanese territorial waters in the past week.
On Thursday, the Defense Ministry said a Chinese navy ship sailed into an area near Kitadaito Island in Okinawa Prefecture, just outside Japan's territorial waters, around 3:05 p.m and left an hour later.
The incident occurred a day after a Chinese navy reconnaissance vessel entered Japanese territorial waters near Kuchinoerabu Island off Kagoshima Prefecture, and a week after a Chinese naval frigate entered the contiguous zone near the disputed Senkaku Islands in the East China Sea. The move near Kuchinoerabu Island was the first such breach by a Chinese military ship since 2004.
"The Chinese military has been unilaterally escalating its actions in the waters near our country," Kishida said at a news conference Friday.
In a separate news conference, Defense Minister Gen Nakatani rapped China for not giving Japan advance warning when its military ships are entering Japan's territorial waters, referring to the incident Wednesday in waters west of Kuchinoerabu Island.
"Generally, there should be a prior communication and notice (given) when a military ship enters territorial waters," Nakatani said.
Nakatani also rebutted Beijing's claim that such prior notification or approval was unnecessary as "each country's vessel has the right of passage" through a strait used for international navigation.
The region into which the Chinese frigate sailed "does not fall under a sea area used for international navigation. Japan cannot accept" China's claims, Nakatani said.