The Philippines dispatched a coast guard plane over the weekend to intercept a Chinese research vessel as it reentered the country’s maritime zone following an extended mission east of Guam.

Ship tracking data released by the Philippine coast guard and confirmed by Newsweek showed the vessel, Xiang Yang Hong 05, spent more than five weeks operating near the U.S. territory before heading back toward the Philippines.

Newsweek reached out to the Chinese Foreign Ministry and the U.S. Seventh Fleet via email for comment outside of office hours.

Why It Matters

China claims nearly all of the South China Sea as its territory, a conduit for an estimated one-third of global maritime shipping. This puts the country at odds with several neighbors, including the Philippines, which since 2023 has stepped up its challenge to China’s expanding presence within the U.S. treaty ally’s exclusive economic zone (EEZ).

An EEZ is an area extending 200 nautical miles (230 miles) from a claimant state’s coast, where foreign fishing and research activities are prohibited without permission under international maritime law.

What To Know

Philippine Coast Guard chief Ronnie Gil Gavan ordered a Philippine aircraft to conduct a maritime domain awareness patrol Saturday in response to the presence of the Xiang Yang Hong 05 off the northeastern tip of Cagayan province, agency spokesperson Jay Tarriela wrote on X.

“The vessel was challenged by the PCG [Philippine Coast Guard] aircraft but did not respond,” Tarriela said.

According to historical ship tracking data, based on satellite technology, the Xiang Yang Hong 05 departed from the southwestern Chinese city of Guangzhou on June 5.

From June 14 to July 24, the vessel sailed back and forth just east of the U.S. EEZ around Guam in a “lawnmower pattern” commonly associated with seafloor mapping.

Guam, home to several major U.S. military bases, sits within the so-called second island chain—a strategic arc stretching from Japan’s Ogasawara Islands to Palau and parts of Micronesia. Washington considers this region a critical second line of defense in the event of conflict with China.

The Xiang Yang Hong 05, which Tarriela described as a former cargo ship, is part of the Xiang Yang Hong family of research vessels whose presence has added to tensions in the maritime zones of China’s neighbors.

It is among three other Chinese ships, including the Xiang Yang Hong 10, the twin-hulled Bei Diao 996 and the Zhuhai Yun, an oceanographic research vessel that doubles as an autonomous drone mothership, that the Philippines tracked in its EEZ last week.

What People Are Saying

Jay Tarriela, Philippine Coast Guard spokesperson Jay Tarriela told local media: “Now in 2025, what is alarming for us—and where we’ve seen a significant increase—is the higher number of Chinese research vessels entering our EEZ [exclusive economic zone].”

“Xiang Yang Hong 05 is just one of the four that we monitored. So imagine if every month we have three or four, it is still alarming.”

A spokesperson for the Chinese embassy in the Philippines, in an August 1 statement: “Ultimately, the reason some Philippine officials repeatedly make statements that distort and attack China’s position is, more likely, an attempt to escalate tensions between the two countries and mislead the international community.”

What Happens Next

Chinese maritime activities, including surveys and coast guard patrols in disputed areas, are likely to remain a point of friction in the South China Sea.

The Philippines is expected to continue challenging these vessels, which analysts have said are meant to normalize Beijing’s sweeping claims.