Vietnam has protested China's recent activities in the disputed South China Sea saying they seriously violate 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 and that China has completed four light houses and is launching the fifth on reefs in the region.

Vietnam Foreign Ministry spokesman Le Hai Binh told reporters that those actions have seriously violated Vietnam's sovereignty and are unlawful.

He says Vietnam demanded that China stop acts that violate its sovereignty and refrain from taking actions that complicate the situation in the South China Sea.

A U.N. arbitration tribunal this week ruled that China's vast territorial claims are violating international maritime law, but Beijing says it doesn't recognize the decision.