Beijing, China - China reasserted its territories around a flashpoint reef in the South China Sea on Sunday, two days after the Philippines defined its own sea boundaries in the contested waters.

Philippine President Ferdinand Marcos on Friday signed two laws defining the country's sea waters and imposing fixed lanes for foreign ships, sparking a sharp riposte by China which summoned Manila's envoy.

Beijing's foreign ministry said in a statement on Sunday that the government had "delimited and announced the baselines of the territorial sea adjacent to Huangyan Dao."

"This is a natural step by the Chinese government to lawfully strengthen marine management and is consistent with international law and common practices," it added.

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Beijing took control of Huangyan Dao, the Chinese name for Scarborough Shoal, in 2012 – a strategic feature in the South China Sea closest to the Philippines.

Beijing has brushed aside an international ruling that its claims to most of the South China Sea have no legal basis.

The Philippines' Maritime Zones Act marks out waters that fall within Manila's territory as well as areas outside of it to which it has maritime entitlements, as agreed by the UN Convention on the Law of the Sea. They include some waters contested by China, which claims almost the entire South China Sea and has brushed off rival claims of several Southeast Asian countries, the Philippines among them.

A second law, the Archipelagic Sea Lanes Act, authorizes the president to impose fixed sea and air routes through which foreign ships or planes may pass "without compromising our national security," Marcos said at the signing ceremony.

Beijing's foreign ministry said that it "firmly opposes" the Philippines' move, which "severely violates China's territorial sovereignty and maritime rights and interests in the South China Sea."

It summoned the Philippine ambassador to Beijing "to lodge solemn representations" over the passage of the laws.

The Philippines has "frequently sent military and coast guard vessels and aircraft...to intrude into the sea and airspace near Huangyan Dao, causing disturbances and provocations," China's coast guard said in a statement on Sunday.

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It vowed to "continue to strengthen patrols and law enforcement in the territorial sea of Scarborough Shoal and relevant waters."

China has in recent months deployed navy and coast guard vessels to bar the Philippines from reefs and islands that Manila says are located within its exclusive economic zone in the sea.

Chinese sailors have rammed, blocked, used water cannons, and even boarded Philippine vessels, causing damage and injuries.

The US has also conducted joint military drills in the area with the Philippines and other countries, exacerbating tensions in the region.