Manila: The Philippines on Sunday filed a formal plea to the United Nations challenging Beijing’s claim to most of the South China Sea, defying Chinese warnings, a day after a dramatic maritime stand-off with the Asian giant.

Philippine Foreign Secretary Albert del Rosario said Manila has filed the plea before a UN arbitration tribunal to declare China’s claims over the strategic and resource-rich waters as a violation of international law.

“It is about defending what is legitimately ours. It is about securing our children’s future. It is about guaranteeing freedom of navigation for all nations,” he told a news conference.

China’s claims over the South China Sea, believed to harbour vast oil and gas reserves, overlap those of the Philippines as well as Brunei, Malaysia, Vietnam and Taiwan.

The Philippines announced last year that it will ask the United Nations to declare China’s claims over the area illegal under the UN Convention on the Law of the Sea. The tribunal had given Manila until Sunday to submit its legal brief.

Chief Philippine government lawyer Francis Jardeleza said he expects the International Tribunal for the Law of the Sea, based in the German city of Hamburg, to advise both parties on the next steps. He did not know when a ruling will be made.

Both officials declined to disclose the specifics of around 4,000 pages of documents that were submitted to the tribunal.

China has refused to take part in the arbitration with its foreign ministry spokesman Hong Lei last week warning that bilateral relations will suffer if the Philippines pursues the appeal.

Hong also said China was “committed to managing and resolving relevant issues (in the South China Sea) through dialogue and consultation”.

Manila has argued that China’s claims cover areas as far as 870 nautical miles (1,611 kilometres) from the nearest Chinese coast and interfere with the Philippines’ exercise of its rights to its continental shelf.

The Philippine filing came a day after a Filipino supply vessel slipped past a blockade of Chinese coastguard vessels to deliver supplies to, and rotate troops from, a remote and disputed South China Sea reef.

The dramatic confrontation took place at Second Thomas Shoal, where a small number of Filipino soldiers are stationed on a Navy vessel that was grounded there in 1999 to assert the Philippines’ sovereignty.

China had said its coastguard successfully turned away a similar Filipino attempt on March 9, forcing the Philippine military to air-drop supplies to the marines.

The Philippine foreign department argues the disputed areas, including the Second Thomas Shoal, are part of the Philippines’ exclusive economic zone and continental shelf over which Manila has sole sovereign rights under the UN sea treaty.

Both China and the Philippines are signatories to the 1982 treaty, but Beijing has repeatedly said it has sovereign rights over the entire Spratlys as well as waters and other islets approaching its neighbours.

It has also accused the Philippines of illegally “occupying” Second Thomas Shoal, which is around 200 kilometres from the western Philippine island of Palawan and about 1,100 kilometres from the nearest major Chinese land mass.

Philippine military spokesman Lieutenant-Colonel Ramon Zagala told AFP on Sunday that authorities were hoping the supply vessel would be able to leave the shoal without further incident after delivering food, water and fresh troops.

“We want them (boat and crew) to safely return,” he said.

The two neighbours are also involved in increasingly frequent confrontations over Scarborough Shoal, another South China Sea outcrop that lies about 220 kilometres west of the main Philippine island of Luzon.