The Philippines urged China on Sunday to call back a 220-strong fleet of fishing boats moored near a disputed South China Sea reef claimed by Manila.

“We call on the Chinese to stop this incursion and immediately recall these boats violating our maritime rights and encroaching into our sovereign territory,” Philippine Defense Minister Delfin Lorenzana said in a statement.

The Philippine Coast Guard spotted 220 fishing vessels believed to be manned by Chinese maritime militia members “moored in line formation” at Whitsun Reef – called Julian Felipe Reef by Manila – on March 7 and reported the sighting to the Armed Forces of the Philippines (AFP).

“The AFP’s Western Command has dispatched Air Force and Navy assets to conduct air and maritime sovereignty patrols to further validate the report,” Maj. Gen. Edgard Arevalo, an AFP spokesman, said on March 21. He did not disclose when the patrols occurred.

“Appropriate reports were made and forwarded to other agencies of government through the [AFP] General Headquarters of such monitored numbers of CMM [Chinese maritime militia],” Arevalo revealed.

Philippine government agencies used the AFP’s reports to take “appropriate actions not limited to filing diplomatic protests,” according to the Marine major general.

“The AFP will not renege from our commitment to protect and defend our maritime interest within the bounds of the law,” Arevalo added.

The Philippine National Task Force on the West Philippine Sea (NTF-WPS) describes Julian Felipe Reef as “a large boomerang-shaped, shallow coral reef.” It is located approximately 175 nautical miles west of the Philippine province of Palawan, which is an archipelago stretching southwest from the western Philippines toward Sabah, Malaysia.

Julian Felipe Reef is positioned within the Philippines’ Exclusive Economic Zone (EEZ) and Continental Shelf (CS), over which Manila has the exclusive right “to exploit or conserve any resources which encompass both living resources, such as fish, and non-living resources such as oil and natural gas,” NTF-WPS noted in a statement issued Sunday.

“Despite clear weather at the time, the Chinese vessels massed at the reef showed no actual fishing activities and had their full white lights turned on during night time,” the statement read. The task force added that the sighting of the Chinese fishing vessels sparked “concern” over the possibility that they may overfish the reef’s waters and damage its marine environment.

“The government will continue to monitor the situation as it remains steadfast in its duty to protect Philippine sovereignty and sovereign rights in the country’s maritime domain,” NTF-WPS said.

“In consonance with the Philippine commitment to the United Nations Convention on the Law of the Sea (UNCLOS), the government shall continue to peacefully and proactively pursue its initiatives on environmental protection, food security and freedom of navigation in the West Philippine Sea as part of its overall national security policy,” the task force added, referring to the section of the South China Sea west of the Philippines.

An independent arbitral tribunal established under UNCLOS found that Beijing’s claims to nearly 90 percent of the South China Sea were illegal in a 2016 case brought by the Philippines. China rejected the ruling and has continued to impose its claim on nearly the entire sea since then.