The Ministry of Foreign Affairs (MOFA) of Vietnam filed a claim to the UN’s Commission on the Limits of the Continental Shelf (CLCS) to extend the limits of its underwater continental shelf in the South China Sea, according to a statement published by the ministry on Thursday.

In its statement, the ministry asserted that Vietnam has “fully legal and scientific bases” to demand the extension of the limits of its extended continental shelf in the central area of the South China Sea beyond 200 nautical miles. The statement also specified that Wednesday’s move aligns with Vietnam’s two previous submissions to the UN: the submission on the extended continental shelf in the North of the South China Sea and the joint Vietnam-Malysia submission on the extended continental shelf in the South of the sea back in 2009.

The MOFA further explained that this decision aims to guarantee Vietnam’s “lawful rights” to its extended continental shelf in accordance with Article 76 of the United Nations Convention on the Law of the Sea (UNCLOS). It further added that the country’s request does not affect the maritime delimitation between Vietnam and neighboring states.

At the end of its statement, the Vietnamese MOFA asserted the country’s sovereignty over the Hoang Sa and Truong Sa Islands, respectively known as the Paracel Islands and the Spratly Islands located in the South China Sea.

Vietnam’s decision to file a submission to the UN to extend the breadth of its continental shelf comes one month after the Philippines filed a similar claim regarding the boundaries of its underwater continental shelf in the South China Sea.

The South China Sea is a disputed region that has witnessed increasing tensions over the last few years, including vessel collisions, environmental accusations and disruptions to maritime navigation.

All these incidents are part of a long-running territorial dispute pitting China against other Southeast Asia countries, particularly the Philippines and Vietnam. China upholds its sovereignty over the South China Sea whereas the Philippines insists that the region is part of its territory. Vietnam is one of the countries that is also concerned by the territorial dispute as it was reported that the country had recently expanded its outposts in the disputed Spratly Islands.

Other foreign countries with indirect interests in the region have also intervened in the confrontations. The US for instance has been conducting military exercises in the South China Sea since 2015 in support of the Philippines, which prompted China to accused the US of undermining stability in the region.