Philippine President Ferdinand Marco Jr signed two laws on Friday to define the country's maritime entitlements and set designated sea lanes and air routes to reinforce sovereignty.
"China firmly opposes this and will continue to take all necessary measures in accordance with the law to resolutely defend China's territorial sovereignty and maritime rights and interests," the foreign ministry said.
Beijing claims sovereignty over nearly all of the South China Sea, including areas claimed by the Philippines, Brunei, Indonesia, Malaysia and Vietnam. China rejects a 2016 ruling by the Permanent Court of Arbitration in the Hague that its sweeping claims were not supported by international law.
The United States, a Philippine ally, backs the court's ruling in the case, which was brought by Manila.
The Chinese ministry's statement on Sunday defined a baseline of "territorial waters" around the Scarborough Shoal, which China claims as its territory and calls Huangyan Island. The shoal is a major point of contention over sovereignty and fishing rights.
China has enacted domestic laws covering the South China Sea, such as a coast guard law in 2021 that allows it to detain foreigners suspected of trespassing.
With an armada of coast guard ships to assert its claims, Beijing routinely accuses vessels of trespassing in areas of the South China Sea that fall inside the exclusive economic zones of its neighbours, and has clashed repeatedly with the Philippines in the past year.
China's coast guard issued a statement on Sunday saying the Philippines has frequently sent military and police warships and aircraft to "intrude" into the waters and airspace near the Scarborough Shoal. It accused Manila of instigating "illegal fishing" in the area.
