Two Chinese aircraft landed on disputed reefs and Beijing's coast guard reportedly blocked a Filipino fishing boat from a contested shoal, in acts of defiance after a landmark ruling found China's vast claims in the South China Sea legally baseless.

Vietnam protested on Thursday that the recent Chinese actions seriously violated Vietnamese sovereignty.

Chinese state media reported that two Chinese civilian aircraft on Wednesday landed successfully on two newly built airstrips on Mischief and Subi reefs. China also said it had completed four lighthouses on disputed reefs and was launching a fifth.

In the Philippines, ABS-CBN TV network reported that Chinese coast guard ships had blocked a Filipino fishing boat from approaching the disputed Scarborough Shoal on Thursday.

ABS-CBN journalist Chiara Zambrano reported that Chinese personnel on two speedboats approached and encircled the Filipino boat carrying her and local fishermen.

One video the network aired showed the Filipino boat being tailed by a white Chinese coast guard ship in an area Zambrano said was a few miles (kilometers) from Scarborough, where the local fishermen were blocked from entering to fish. Another video showed the Chinese personnel riding a speedboat, using a bullhorn and ordering the Filipinos to leave "this area immediately."

Mayor Arsenia Lim of the northwestern Philippine town of Masinloc, where the fishermen live, said they sailed to Scarborough to test China's compliance with the ruling.

"What they're doing is bad because it shows as if there is no law," Lim told The Associated Press by telephone. "Our government should defend the livelihood of these people because it's the only place where they get their income."

The ruling Tuesday from the Permanent Court of Arbitration in The Hague, Netherlands, was based on the 1982 U.N. Convention on the Law of the Seas, which both China and the Philippines have ratified. The Philippines brought the case to arbitration in 2013 after witnessing China's activities in Scarborough and elsewhere in the sea, which is rich with fish and potential energy resources.

Beijing boycotted the case entirely and declared the ruling null and void. China prefers one-on-one negotiation to settle its territorial disputes, though its smaller, poorer neighbors see that approach as imbalanced. Six governments have overlapping claims to the South China Sea, and Beijing's use of its coast guard, building of artificial islands and other activities to cement its claims have raised international concerns.

Vietnam Foreign Ministry spokesman Le Hai Binh demanded Beijing cease actions that complicate the situation.

"Despite the opposition of Vietnam and concerns by the international community, those actions conducted by China have seriously violated Vietnam's sovereignty and are unlawful and cannot change the fact about Vietnam's sovereignty over the Hoang Sa and Truong Sa archipelagoes," Binh told reporters, referring to the Paracel and Spratly chains of islands and reefs.

Binh reiterated that Vietnam has all "legal basis and historical evidences" to affirm its sovereignty over both chains.

In Beijing, Chinese Foreign Ministry spokesman Lu Kang said Thursday that if anyone challenged China's interests with provocative actions, "China will surely make a resolute response."