"On August 22, two Philippine military aircraft trespassed into the airspace near the Nansha Islands, including Zhubi Jiao (Subi Reef), where China is stationed," Beijing's foreign ministry told AFP in a statement.

It added that "the Chinese side took necessary countermeasures in accordance with the law, in order to protect its own sovereignty and security".

The foreign ministry did not specify what types of measures China took, describing the actions as "professional, restrained, and standardised".

"China will continue to firmly protect its own territorial sovereignty and maritime rights, and firmly oppose any infringing actions," it added.

Beijing claims almost the entire South China Sea despite an international tribunal ruling that its assertion has no legal basis.

China and the Philippines have had repeated confrontations in the waters in recent months, including around a warship grounded years ago by Manila on the contested Second Thomas Shoal.

Earlier this week, both countries confirmed that coast guard ships had collided in a pre-dawn incident near the disputed Sabina Shoal, located 140 kilometres (86 miles) west of the Philippine island of Palawan and about 1,200 kilometres from Hainan island, the closest Chinese landmass.