The Philippines' defence chief has demanded 200 Chinese vessels, which he says have militias onboard, leave a hotly-contested reef in the South China Sea claimed by both China and Manila.
The country's foreign secretary added they will "fire at will" as tensions between the two nations intensify.
Whitsun Reef, known as Julian Felipe by Manila, is a shallow coral area 324km west of Bataraza in the western Philippine province of Palawan.
It is within the Philippines' exclusive economic zone - which according to the government watchdog which oversees the reef means the country "enjoys the right to exploit or conserve any resources".
On Saturday the government watchdog said it had spotted 200 Chinese vessels moored there on March 7, releasing photos of the boats lined up on the waterway.
According to AP, it said it was a "concern due to the possible overfishing and destruction of the marine environment, as well as risks to safety of navigation" - although adding the boats were not actually seen fishing when located.
Philippines defense chief Delfin Lorenzana on Sunday said the country calls on China to "stop this incursion and immediately recall these boats violating our maritime rights and encroaching into our sovereign territory".
Philippines foreign secretary Teodoro Locsin also tweeted on Sunday saying they had filed a diplomatic protest over the Chinese presence.
"I got the coordinates, so to speak. And relayed to my legal artillery, 'Fire at will'," Locsin's tweet reads.
"Shell should be flying at first light. I don't usually announce maneuvers but it seems everybody is baring his chest."
AP reports Chinese fishing boats have, for a long time, been suspected to be manned by militia to carry out Beijing's territorial claims. This means the 200 boats taking over the reef is causing great concern for the Philippines.
Chinese embassy officials have not issued a comment over the dispute. China and the Philippines have been in a territorial standoff over the waterway, alongside four other governments for decades.