Chinese Ships 'Swarming' Whitsun Reef. Here's What to Know | TIME

Some 135 Chinese vessels were spotted near Whitsun Reef off the coast of the western Philippine island province of Palawan this weekend. Although it remains unclear exactly what the vessels are doing there, experts tell TIME that it’s likely the latest Chinese display of maritime power in the hotly contested waters of the South China Sea.

“The whole idea is to project presence,” says Collin Koh, an expert in naval affairs at the S. Rajaratnam School of International Studies in Singapore. “That, ‘I'm there and there's nothing you can do to chase me away.’”

Here’s what we know about the Chinese boats.

Commodore Jay Tarriela, a spokesperson for the Philippines coast guard, said the vessels were spotted in the Whitsun Reef, known locally as the Julian Felipe Reef.

PCG MONITORS ILLEGAL PRESENCE OF MORE THAN 135 CHINESE MARITIME MILITIA VESSELS IN JULIAN FELIPE REEF

On November 13, the PCG monitored 111 Chinese Maritime Militia (CMM) swarming the area of Julian Felipe Reef, and this number increased to 125 based on the last monitoring of… pic.twitter.com/hlFvaOWW2z

In response, National Security Adviser Eduardo Año ordered the coast guard to patrol the area and challenge what he called the “illegal presence” of the Chinese vessels there. Under international maritime law, the Philippines has sovereign rights over waters 200 nautical miles off the coast, which the Whitsun Reef falls within.

Read More: China Is Testing How Hard It Can Push in the South China Sea Before Someone Pushes Back

More than a dozen of the vessels were reportedly rafted together. Koh says this is either to weather strong conditions at sea or thwart law enforcement forces, with the other scattered hulls securing the perimeter of the reef.

It’s not clear what the vessels are doing there—China has yet to comment on them. According to Tarriela’s statement, the PCG radioed the Chinese vessels swarming about, but they received no response.

China has laid claim to virtually all of the South China Sea, a waterway that carried $3.4 trillion in global trade in 2016.

Wary of inviting criticism and invoking armed conflict, analysts say China resorts to “gray zone” tactics: responses that fall short of what