The government said Monday it will respond firmly after Chinese vessels intruded 14 times into Japanese territorial waters near the Senkaku Islands in the East China Sea over the weekend, stoking bilateral tensions.
Chief Cabinet Secretary Yoshihide Suga said Japan will continue to urge China not to escalate the territorial dispute, while also responding firmly and calmly.
Suga told a news conference that 14 Chinese government vessels had entered the "contiguous waters," which can be policed for customs and immigration violations, in recent days and intruded into what Japan considers its territorial waters 14 times.
Twelve Chinese vessels remained in the area early Monday, he said. Agencies including the Japan Coast Guard would act together closely to deal with the situation, Suga said.
Chinese activity near the uninhabited islets has heated up since Friday, prompting repeated Japanese protests, including three on Sunday alone.
Some 230 Chinese fishing vessels were also in the area on Saturday, the Foreign Ministry said in Tokyo.
The incidents come amid heightened tensions after an arbitration court in The Hague invalidated China's sweeping claims in the disputed South China Sea less than a month ago, in a case brought by the Philippines.
China has refused to recognize that ruling. Japan called on China to adhere to the verdict, which it called binding. This prompted Beijing to warn Tokyo not to interfere.
On Saturday, Chinese Foreign Ministry spokeswoman Hua Chunying said in a statement on the ministry's website that China had indisputable sovereignty over the islands and nearby waters.
China accused Japan's new defense minister, Tomomi Inada, on Friday of recklessly misrepresenting history after she declined to say whether Japanese troops had massacred civilians in China during World War II.
Inada echoed Suga's comments Monday, saying Japan's military would conduct air patrols to provide information to the Coast Guard.