China passed legislation on Friday allowing its coast guard to use “all necessary means” to stop or prevent threats from foreign vessels, including demolishing other countries’ structures built on Chinese-claimed reefs.

“After reflection, I fired a diplomatic protest,” Philippines’ Foreign Minister Teodoro Locsin, said on Twitter.

“While enacting law is a sovereign prerogative, this one — given the area involved or for that matter the open South China Sea — is a verbal threat of war to any country that defies the law; which, if unchallenged, is submission to it,” he added.

China’s embassy in Manila did not immediately respond to a request for comment.

The law, which permits the coast guard to board and inspect foreign vessels in waters China considers its own, could pose problems given the scope of Beijing’s territorial claims in the South China Sea.

China’s claim of 90% of the strategically important waterway was invalidated by an international arbitration tribunal in 2016, but it does not recognise that ruling.

China maintains a constant coast guard presence hundreds of kilometres off its mainland, near the disputed islands and often within the Exclusive Economic Zones (EEZ) of its neighbours, some of which accuse the vessels of aggressive behaviour, like disrupting fishing and energy exploration activities.

Taiwan, Malaysia, Vietnam, the Philippines and Brunei also have competing claims with China.

The Philippine protest comes days after ally the US sent a carrier group through the waterway to promote “freedom of the seas”.

China on Tuesday said it would hold military drills of its own this week.

A spokesman for President Rodrigo Duterte on Monday said the Philippines hopes no country will do anything to increase tensions.