A Chinese H-6K bomber patrols islands and reefs in the South China Sea. (Liu Rui/Xinhua via AP)

The Philippines has asked China to explain the presence of a larger-than-usual number of ships near the Scarborough Shoal, raising the prospect of fresh tension in the South China Sea. 

With the Group of 20 leaders gathered in the southern Chinese city of Hangzhou, a Philippine Air Force overflight reportedly spotted at least eight ships near the disputed shoal, including four Chinese coast guard vessels, two barges and two boats that could be troop carriers, according to the Department of National Defense. 

Defense Secretary Delfin Lorenzana on Sunday expressed “grave concern” about the number and nature of the vessels, saying the presence of barge-like ships could signal Chinese plans to dredge — and potentially build — in the area.

In a regular press briefing on Monday, Hua Chunying, a spokeswoman for China’s Foreign Ministry, downplayed the idea of a change in policy or posture. “The situation has not changed,” she said.

Yet the timing and nature of the Filipino reports make the news tough to ignore. 

Since July, when a European court ruled there is no legal or historical basis for China’s claims to most of the South China Sea, the Scarborough Shoal has been seen as a likely hotspot.

The shoal, known as Panatag in the Philippines and Huangyan Island in China, is located about 120 miles from the Philippine coast, close to the former U.S. military base at Subic Bay, where a growing number of U.S. ships now dock. 

China seized controlled of Scarborough in 2012 and has since angered Manila by chasing out Filipino fishermen. In July, the Permanent Court of Arbitration ruled that barring Filipinos from the shoal violated “traditional fishing rights” — but the Chinese did not budge.

Many foreign experts and diplomats believe China may ultimately build on Scarborough, potentially turning it into a military outpost, just as they have done in the nearby Spratly Archipelago

But most believed China would wait until after this week’s G20 meetings, or even after the U.S. presidential election, to make any move. The fact that new ships were reported the day before China’s Xi Jinping had tea with President Obama in Hangzhou is therefore something of a surprise. 

In Beijing on Monday, Hua, the spokeswoman, warned against seeing a message in the timing. “We hope the situation won’t be hyped up,” she said.