Beijing has marked out 25 islands, shoals, and reefs in the South China Sea that covers Vietnam’s Hoang Sa (Paracel) and Truong Sa (Spratly) archipelagoes.

An aerial view of an island in the Paracel chain, which China illegally considers to be its territory. Photo: AFP

The statement came a day after China said it set up two administrative districts namely Xisha and Nansha to govern Paracel and Spratly, according to the South China Morning Post.

Many of the newly-named islands fall within the two new districts.

Naming geographical features is part of China’s activities to cement its territorial claims in the face of increasing opposition from Vietnam.

China also named 55 underwater locations to claim rights over resources, saying it has been conducting scientific surveys of many of the unnamed areas.

Last month, Vietnam sent a diplomatic note to the United Nations to protest against China’s sovereignty claims over the South China Sea.

China and other claimants in the South China Sea. Source: UNCLOS, CIA. Photo: BBC

China claims almost the whole South China Sea, but these claims are not recognized by its neighbors and most other countries. Other claimants namely Vietnam, the Philippines, Taiwan, Malaysia, and Brunei have also competing claims over territory.

China has continued establishing military outposts on artificial islands.

The reports of increased Chinese activity in the sea recently, including the sinking of a Vietnamese fishing boat and a seismic survey ship’s traveling into Vietnamese and Malaysian waters has prompted US officials to warn Beijing against “provocative actions” in the sea, the Express reported.

In a statement, the US State Department said “The United States is concerned by reports of China’s repeated provocative actions aimed at the offshore oil and gas development of other claimant states. “In this instance, [China] should cease its bullying behavior and refrain from engaging in this type of provocative and destabilizing activity.”

Vietnam’s Foreign Ministry Spokeswoman Le Thi Thu Hang has since accused China of violating its sovereignty.