"The Diaoyu islands are an integral part of China. China has historic and legal rights to sovereignty over these islands. Japan's actions can in no way change this objective reality. We urge the Japanese side not to create artificial incidents around Diaoyu and make efforts jointly with China to improve bilateral relations in the spirit of a consensus reached in 2014," Chinese Foreign Ministry's spokesman Lu Kang said Thursday.
Earlier in the day, the Japanese Kyodo news agency reported, citing the country's Defense Ministry, that a Chinese frigate and an unidentified foreign submarine had been detected outside Japanese territorial waters near the islands.
"We want to strongly urge China not to do anything to interfere with improving bilateral ties," Chief Cabinet Secretary Yoshihide Suga said at a news conference.
In addition, director-general of the Japanese Foreign Ministry's Asian and Oceanian Affairs Bureau Kenji Kanasugi met with Chinese ambassador Cheng Yonghua, protesting the incident.
According to Chinese Defense Ministry statement, its missile frigate had responded to two Japanese ships entering its claimed waters.
Beijing strongly opposes Japanese actions, which had hyped up China's actions and "mixed up right and wrong", the statement says.
Japan and China have been engaged in a territorial dispute over the islands since the 1970s. China says that the islands have been part of its territory since ancient times, while Japan argues the islands have been in its control since 1895. In 2014, the sides issued a joint four-point consensus on improving bilateral ties.