The Philippines on Thursday warned Beijing to "back off" and condemned the "illegal" actions of three Chinese coast guard vessels that it said blocked the passage of two of its supply boats and fired water cannons.

The supply boats were transporting food supplies to military personnel in Ayungin Shoal (Second Thomas Shoal) in the South China Sea, Foreign Secretary Teodoro Locsin said in a statement.

"Fortunately, no one was hurt; but our boats had to abort their resupply mission," Locsin said, adding that he had "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 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," he added.