THE Atin Ito (This is Ours) coalition on Monday started its sail to Philippine-occupied Thitu Island (Pag-asa Island), where it plans to hold a concert. — PHILIPPINE STAR/MICHAEL VARCAS

THE Armed Forces of the Philippines (AFP) on Tuesday said it is prepared to respond and help a civilian-led sail in the South China Sea (SCS) after Chinese Coast Guard vessels shadowed and challenged the mission 100 kilometers off the coast of El Nido, Palawan.

“There are appropriate contingencies in place in the event that the AFP’s response is needed,” Philippine Navy spokesman Rear Admiral Roy Vincent T. Trinidad told a news briefing in mixed English and Filipino.

The Atin Ito (This is Ours) coalition on Monday started its sail to Philippine-occupied Thitu Island (Pag-asa Island), where it plans to hold a concert.

While aboard the 115-meter M/V Kapitan Felix Oca, the coalition said two Chinese Coast Guard vessels started shadowing and challenging the ship via radio on Tuesday morning.

The Chinese ships were spotted tailing the Philippine vessel as close as 7.4km, the Philippine Coast Guard (PCG) said in a separate statement.

“In response to the unauthorized patrol by the China Coast Guard (CCG), the PCG vessels have initiated radio communications to challenge CCG 3306’s claim of operating under the jurisdiction of the People’s Republic of China,” it added., referring to one of the Chinese ships that followed the Philippine vessel.

The Chinese Embassy in Manila did not immediately reply to a Viber message seeking comment.

Mr. Trinidad said the military had not received any request for support from the civilian ship, but maintained that they are in “close coordination” should the need arise.

China would likely deploy numerous vessels near Thitu in the Spratly Islands during the civilian sail, he added, noting its closeness to heavily militarized and Chinese-occupied Subi Reef.

The reef has a runway, hangars, radar domes and served as a port for Chinese ships deployed in the region.

The Philippines keeps a military outpost on Thitu island — the second-largest island in the disputed Spratly Islands, a region that lies at the center of long-standing maritime tensions in the South China Sea involving China, Vietnam, Brunei, Malaysia and Taiwan.

Competing claims in the South China Sea have led to frequent confrontations between Philippine and Chinese forces, and both nations have tried to assert their sovereignty through their naval presence and infrastructure build-up.

Tensions between Manila and Beijing flared again last week after a Chinese coast guard ship used a water cannon on a Philippine civilian ship and bumped against it at Sandy Cay, which is near Thitu Island.

Mr. Trinidad urged other civil society groups to organize similar activities in the South China Sea to help shore up support for the Philippine government’s claim over the waterway.

“We would also like to encourage other civic society groups to show their support to the government’s stand in the West Philippine Sea by conducting similar activities that would send such message,” he said.

China claims nearly all of the potentially mineral- and oil-rich South China Sea based on a 1940s nine-dash line map that overlaps with the exclusive waters of the Philippines and neighbors like Vietnam and Malaysia.

A United Nations-backed tribunal in 2016 voided China’s sweeping claims for being illegal, a ruling that Beijing does not recognize. — Kenneth Christiane L. Basilio