The Japanese government said on Tuesday that it has lodged a protest with China for installing a buoy inside Japan's exclusive economic zone near the Senkaku Islands in the East China Sea and is demanding the immediate removal of the object.

Chief Cabinet Secretary Hirokazu Matsuno told a press conference that the Chinese act is inconsistent with international law. The buoy was found in July near the uninhabited, Tokyo-controlled, Beijing-claimed islets.

China has been intensifying its military activities and maritime assertiveness in the East and South China seas, with Japan protesting against repeated intrusions by Chinese ships into Japanese waters around the Senkakus.

"Installing structures in our nation's EEZ without our consent violates regulations related to the U.N. Convention on the Law of the Sea," Matsuno, the top government spokesman, said, referring to an international agreement whose signatories include Japan and China.

He added that the Japan Coast Guard has issued a navigation warning since July 15 to ensure the safety of ships sailing in nearby waters.

According to the Japanese Foreign Ministry and other sources, a yellow buoy was spotted in the waters about 80 kilometers northwest of Uotsuri, the Senkakus' largest island, with a light and Chinese characters suggesting that its purpose is for marine research.

Japan last confirmed a buoy set up by China around the Senkakus in 2018.

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