Philippine President Rodrigo Duterte says China may already be building structures at Scarborough Shoal in the South China Sea, one of Asia's most dangerous flashpoints.
In a speech at the inauguration of a new port in Davao del Norte province yesterday, Mr Duterte said a report he received from the Philippine Coast Guard showed that "there are a lot of barges" around Scarborough.
He said the report suggested that "there is construction somewhere".
"What is the purpose of a barge? You put something there and bring it somewhere usually," he said. "I think they are starting (at Scarborough), and (there) would be another ruckus there."
This is the first time reports about China trying to reclaim land at Scarborough have surfaced since an international tribunal at The Hague struck down China's claims to the South China Sea on July 12. China claims nearly all of the South China Sea, where about US$5 trillion (S$6.8 trillion) of seaborne trade passes annually. Brunei, Malaysia, the Philippines, Taiwan and Vietnam also have claims on parts of the sea.
China seized control of Scarborough after a two-month stand-off with the Philippines in 2012, which began when a Philippine Navy frigate seized eight Chinese fishing boats suspected of poaching coral and giant clams around the shoal.
What is the purpose of a barge? You put something there and bring it somewhere usually. I think they are starting (at Scarborough), and (there) would be another ruckus there.
PHILIPPINE PRESIDENT RODRIGO DUTERTE, on reports of Chinese activity at Scarborough Shoal.
The United States eventually mediated a deal. Both sides were told to withdraw from Scarborough.
The Philippines pulled out its ships, but China stayed and later roped off the mouth of the lagoon, sealing off the entire atoll.
Since then, China has been chasing fishermen from the Philippines away from Scarborough.
In March, US President Barack Obama warned Chinese President Xi Jinping that there would be serious consequences if China reclaimed land at Scarborough, located just 220km west of the main Philippine island of Luzon.
Mr Obama raised the stakes with Mr Xi after US intelligence concluded that China was moving towards reclaiming land at the shoal.
Some officials worry that China may install radars and missiles there. Along with facilities in the Paracel and Spratly islands, that would enable China to create a strategic triangle, which could threaten the US military presence in Hawaii and Guam.
Asean and China are expected to sign at next week's Asean summit in Laos an agreement to establish hotlines and adopt communications protocols to avoid potential naval clashes in the South China Sea, said Foreign Affairs Assistant Secretary Helen de la Vega.
The Code for Unplanned Encounters at Sea "is one way of de-escalating tensions in the South China Sea", she said.
A senior Philippine Navy commander told Reuters: "This is very important because any accident that can lead to a major confrontation will be avoided if our navies and coast guards are communicating with each other."
He said there had been instances when Chinese vessels had not responded to radio and signal communications when they encountered a Philippine Navy ship.
Mr Duterte is holding nine bilateral talks at the summit, including with Mr Obama, Russian leader Vladimir Putin and Japanese Prime Minister Shinzo Abe.
China's foreign ministry said yesterday it was open to a meeting with Mr Duterte at the summit, but no meetings had been scheduled with Chinese Premier Li Keqiang or United Nations Secretary-General Ban Ki Moon.