The Philippines on Wednesday released photos purporting to show Chinese boats near a shoal in the South China Sea, claiming that the presence of new ships in the area could signal another attempt by Beijing to build in disputed fishing grounds.
The outcry could add further tensions during a summit of U.S. and Southeast Asian leaders in Laos over China’s reach into the South China Sea, where Beijing has already constructed artificial islands and other facilities that the West and allies fear could be used as a military foothold in the region.
China claims it has sovereignty over the sea, which borders the Philippines and several others nations that have sharply challenged Beijing’s push in the area. The United States also has raised concerns about possible Chinese attempts to limit fishing rights and shipping lanes in the sea.
In July, the Permanent Court of Arbitration in The Hague ruled against China’s assertion of control over the South China Sea. China has refused to recognize the ruling.
The latest move by the Philippines came two days after its Defense Ministryexpressed “grave concern” about the presence of a larger-than-normal number ships in the area, and just hours before U.S., Chinese and Southeast Asian leaders met for the Association of Southeast Asian Nations (ASEAN) summit.
The pictures from the Scarborough Shoal — a small grouping of rocks in rich fishing grounds — may add a new dimension to an already awkward summit in which Philippine President Rodrigo Duterte used the Tagalog term for “son of a whore” in railing against President Obama and perceived American interference in Philippine affairs. Obama then canceled a meeting with Duterte.
So far this week, the Chinese side has tried to downplay the Philippine claims. Asked on Monday about the presence of new ships, a spokeswoman for China’s Foreign Ministry said there has been no change in China’s policy or posture and urged reporters not to “hype” the matter.
But observers within and beyond the Philippines say it is hard to ignore what could be a move to strengthen China’s presence in the area — or signal that it can strengthen its presence if and when it chooses.
“These pictures are extremely alarming, lending credence to reports by sources in China indicating that Beijing was planning to build facilities in the Scarborough Shoal,” said Richard Javad Heydarian, an assistant professor of political science at Manila’s De La Salle University.
“If China indeed pushes ahead with actual construction, it could lead to collapse in burgeoning negotiations between the Duterte administration and Beijing." 
The problem, experts said, is that it is hard to tell from the pictures alone what the Chinese ships can do — dredge, lay cable, fish — or why the Chinese side may have sent them.
In its initial comments on the matter, the Philippine Defense Ministry said the vessels included Chinese coast guard ships, barges that could be used for dredging, and potential “troop carriers.”
Academics and analysts who follow the conflict closely said the pictures alone do not prove that to be true.
“It’s hard to draw any conclusion yet,” said Yanmei Xie, a Beijing-based analyst at the International Crisis Group, "But I'd be skeptical that China would choose to start dredging while the G-20 is ongoing and on the eve of the ASEAN summit."
“It looks like a mixture of coast guard ships and fishing vessels — hardly the precursor of a massive reclamation project,” said Ian Storey, a senior fellow at the ISEAS-Yusof Ishak Institute in Singapore.
But Storey said it could put Duterte in a difficult spot.
“As only America can help the Philippines push back against China and protect its maritime claims, Duterte may well come to regret insulting President Obama," he added.