MANILA—The Department of Foreign Affairs said Chinese Coast Guard vessels blocked Philippine supply boats in the Ayungin Shoal.
In a statement posted early Thursday, the DFA said Western Command in Palawan reported that 3 Chinese vessels “blocked and water cannoned” 2 Philippine supply boats in Ayungin on Tuesday.
The boats were supposed to transport food supplies to military personnel in the area.
"Fortunately, no one was hurt; but our boats had to abort their resupply mission," Foreign Secretary Teodoro Locsin Jr. said in a statement.
"I have conveyed in the strongest terms to H.E. Huang Xilian, Ambassador of China and to the Ministry of Foreign Affairs in Beijing our outrage, condemnation and protest of the incident."
The DFA said such acts were illegal, because they were in Philippine territory.
"Ayungin Shoal is part of the Kalayaan Island Group (KIG), which is an integral part of the Philippines, as well as the Philippines’ exclusive economic zone and continental shelf, and over which the Philippines has sovereignty, sovereign rights and jurisdiction," Locsin said.
"The acts of the Chinese Coast Guard vessels are illegal. China has no law enforcement rights in and around these areas. They must take heed and back off."
Locsin said these recent developments threatened China-Philippines relations.
"This failure to exercise self-restraint threatens the special relationship between the Philippines and China that President Rodrigo R. Duterte and President Xi Jinping have worked hard to nurture," he said.
"The Philippines will continue to provide supplies to our troops in Ayungin Shoal (Second Thomas Shoal). We do not ask permission to do what we need to do in our territory."
On Wednesday, the Philippines and the United States reiterated that the 2016 ruling of a UN-backed arbitration court that invalidated China’s expansive claims in the resource-rich South China Sea is legally binding to both Manila and Beijing.
In October, the DFA said it protested what it regarded as fresh "provocative acts" by Chinese vessels in the South China Sea.
The Philippines has so far filed 211 diplomatic notes against China since Duterte came to power amid its continuing incursions in the country's waters, the DFA also said.
"As we have in the past, we will continue to assert our sovereignty, sovereign rights, and jurisdiction over our territory," Cabinet Secretary and acting Malacañang spokesman Karlo Nograles said in a statement on Thursday.
Earlier this year, hundreds of Beijing's ships were also spotted around the West Philippine Sea, the country's EEZ in the vast, resource-rich South China Sea.
Philippines authorities described their presence as an incursion.
The Philippine Coast Guard (PCG) has been conducting patrols in the West Philippine Sea.
Beijing maintains a constant presence of coast guard and fishing boats in the international waterway to assert its claim of sovereignty, including hundreds in the Spratly islands, where Brunei, Taiwan, Vietnam and Malaysia also have claims.
This is despite the Arbitral Tribunal in 2016 concluding that there is no legal basis for China to claim historic rights to resources within the sea areas falling within its so-called "9-dash line.”
China has refused to recognize the Award, calling it “illegal, null and void.”
Duterte has refused to press China to follow the court's ruling, as he pursued investments and loans from the economic superpower.
In May, Duterte called the arbitral award a scrap of "paper" that belongs to the wastebasket. But that same month, he said he would not withdraw Philippine ships from the waterway.
Analysts and several countries earlier warned China of its incursions in the West Philippine Sea, as it could threaten regional stability.