China has accused the Philippines of violating a 13-year-old informal code of conduct in the South China Sea with building work on disputed islets, hitting back after repeated criticism of China's own construction work.
China and the 10-member Association of South East Asian Nations (ASEAN) signed an agreement in 2002 to refrain from occupying uninhabited reefs and shoals in the sea, and from building new structures that would complicate disputes.
In a statement released just before midnight on Monday, China's Foreign Ministry urged the Philippines to stop its "malicious hyping and provocation" in the dispute, whose basis, it said, was Manila's illegal occupation of certain Chinese islands.
"The Philippines side has conducted large-scale construction of military and civil facilities including airports, ports and barracks on those islands for many years," the ministry said.
The statement was issued after the Philippines Foreign Ministry said it was China that had violated the code with its construction and was accusing Manila of violations to justify and provide cover for Chinese reclamation work.
"China has never, ever taken actions that may complicate and deteriorate the disputes or affect regional peace and stability," the Chinese ministry said, urging Manila to stop all building work and evacuate its people.
Disputes over how to tackle an increasingly assertive stance by China - an ally of several Southeast Asian states - in the strategic South China Sea make the issue the region's biggest potential military flashpoint.
China last week accused Vietnam, the Philippines and others of carrying out their own illegal building work.
China claims 90 percent of the South China Sea, which is believed to be rich in oil and gas, which conflicts with overlapping claims from Brunei, Malaysia, the Philippines, Vietnam and Taiwan.
Recent satellite images show China has made rapid progress in building an airstrip suitable for military use in the disputed Spratly Islands and may be planning another.
Those moves, along with other reclamations, have caused alarm around the region and in Washington too.