“The seabed and the subsoil extending from our archipelago up to the maximum extent allowed by Unclos hold significant potential resources that will benefit our nation and our people for generations to come,” Philippine Foreign Assistant Secretary Marshall Louis Alferez said in a statement.

Unclos is the 1982 United Nations Convention on the Law of the Sea, which grants exclusive rights to exploit natural resources in continental shelf to a coastal state.

The move by the Philippines drew swift opposition from Beijing, which urged the commission not to review Manila’s submission as it involved disputed maritime space.

China’s foreign ministry spokesperson Lin Jian said on Monday that the commission should not consider or qualify the submission by the Philippines if it involves delimitation of disputed waters, in line with the rules of procedure of the CLCS.

Lin said Beijing was still gathering information, but Manila’s “unilateral submission” of an extended continental shelf infringes upon China’s sovereign rights and jurisdiction.

Maritime affairs experts held similar views, predicting that Manila’s bid was unlikely to succeed, and Beijing would view the move as a legal challenge that further complicated the South China Sea disputes.

Beijing would see the claim as “another legal and political challenge from Manila” just like the 2016 South China Sea arbitration, and view it as an attempt to undermine China’s extensive claims using a UN institutional approach, he added.

Mainland China claims almost the entire South China Sea, including parts claimed by the Philippines, Brunei, Malaysia, Taiwan and Vietnam.

In 2016, an international tribunal ruled in favour of the Philippines, dismissing China’s broad claims as having no legal basis. However, Beijing has rejected and criticised the ruling.

Experts said that even though the details of Manila’s submission had not yet been made public, its continental shelf claims might overlap with those of other coastal states in the South China Sea, and could potentially propel other claimant states to adopt similar tactics.

“The Philippines’ submission could be a potential risk that sets a precedent for other claimant states, and they may file similar ECS (extended continental shelf) submissions to assert their rights,” said Ding Duo, an associate research fellow at the National Institute for South China Sea Studies in Hainan.

He added that claimant countries could file their submissions separately, but joint submissions were also possible, and either situation would further complicate the South China Sea disputes.

“This will make the dispute even more complex and harder to resolve, and introduces a new point of contention for how Beijing and Manila should properly manage and handle their differences in the South China Sea,” Ding said.

“In a nutshell, Manila’s doings add more complexity to the already complicated South China Sea disputes, rather than simplifying it.”

But Lucio Pitlo III, the president of the Philippine Association for Chinese Studies, said the Philippines’ latest move and the 2016 arbitration were part of its efforts to use international law to protect its maritime claims.

“Both will affect the interests of other disputants in the semi-enclosed sea, although officially, the 2016 ruling only binds Manila and Beijing, a judgment China continues to reject. In like manner, a unilateral ECS submission may also impact the interests of other littoral states,” he said.

Maritime observers predicted that Beijing would retaliate against Manila with tough operational and diplomatic measures.

“China might also increase the intensity of their interdictions at Second Thomas Shoal or escalate elsewhere in the South China Sea against Philippines interests,” Carnegie’s Kardon said, adding that China might also choose to publish baselines around the Spratlys to refute the Philippines’ claims.

Baselines are an important concept in defining maritime boundaries and asserting jurisdictions over resources, which act as the starting points from which a country’s territorial sea, exclusive economic zone, and continental shelf are measured.

Beijing could opt for stronger countermeasures to safeguard its rights at sea, especially during stand-offs with Philippine vessels in the South China Sea, according to Ding.

“Beijing believes it is crucial to make Manila pay a price for its actions, or else it will continue to provoke and hit the nerve repeatedly,” he said.

02:37

Philippine admiral at centre of ‘new deal’ saga breaks silence on alleged South China Sea pact

Philippine admiral at centre of ‘new deal’ saga breaks silence on alleged South China Sea pact

Ding said the move was a clear demonstration of Beijing’s resolve to implement effective control measures in response to the Philippines’ actions.

Quoting an anonymous source, the Philippine media reported that China Coast Guard towed one of the Philippines’ boats and confiscated the crew’s firearms during the Monday run-in, while also injuring some Filipino crew members.