PUERTO PRINCESA, Philippines -- China is pressing ahead with the construction of artificial islands on at least two reefs that are also claimed by the Philippines in an increasingly tense territorial dispute, Filipino officials said Friday, despite Beijing's pronouncement that some work would end soon.
Mayor Eugenio Bito-onon of Kalayaan islands, which are under Philippine control, said he saw Chinese construction in full swing with many dredgers and huge cranes visible when he flew last week near Subi Reef.
It's one of at least seven reefs and atolls in the South China Sea where the U.S. and the Philippines have expressed concern that China's island-building could be used to base military planes and navy ships to intimidate other claimants, reinforce China's claim over virtually the entire area and threaten freedom of navigation in one of the world's busiest shipping lanes.
"It's full-blast construction. It's massive and incredible," Bito-onon told The Associated Press, adding that it was evident it would take months before the Chinese complete the work.
In the mid portion of the emerging man-made island, a 3-kilometer (1.9-mile) -long landfill is taking the shape of a runway, he said.
His comments followed similar findings by the U.S. military and independent defense analysts.
Two senior Philippine military officials, speaking on condition of anonymity because they weren't authorized to talk to the media, said that aside from Subi Reef, China's island-building has also continued on Mischief Reef in the Spratly Islands, based on recent military surveillance.
Chinese Embassy officials in Manila did not immediately comment.
The Chinese Foreign Ministry said on June 16 that the land reclamation projects on some islands and reefs "will be completed in upcoming days." However, in a sign that the developments were far from over, the ministry also said on its website that China would follow up by building infrastructure for maritime search and rescue, environmental conservation and scientific research.
Asked when the island-building would be completed, Chinese Defense Ministry spokesman Senior Col. Yang Yujun gave a vague reply to reporters Thursday, saying it "depends on the progress made on the ground."
Chinese Foreign Ministry spokesman Lu Kang said island construction projects "do not affect the freedom of navigation and overflight enjoyed by all countries in accordance with international law in the South China Sea."
However, a U.S. Navy plane flying near one of the artificial islands last month was told to leave the area by the Chinese military. In a separate incident several weeks ago, a Philippine air force plane was also ordered by the Chinese navy to leave the area. The incidents raised fears that China was preparing to enforce an air defense identification zone over the South China Sea, similar to one it declared over disputed Japanese-held islands in the East China Sea in 2013.
The U.S. argues that China can't use artificially constructed islands to expand its sovereignty. U.S. officials have said they were considering stepping up patrols to ensure free navigation in the contested region and have defied Beijing's warning for Washington to stay out of the Asian disputes.
"We are committed to operate safely in international waters as we believe every nation has the right to do and we look forward to operating throughout Southeast Asia," U.S. Navy Capt. Fred Kacher, who helped oversee annual exercises between U.S. and Philippine navies that ended Friday on western Palawan island, told AP.
The coastal combat ship USS Fort Worth and a P-3 Orion surveillance plane joined the gunnery and missile defense drills with Filipino counterparts in the Sulu Sea east of Palawan this week after completing patrols in the South China Sea, according to U.S. military officials.
The convergence of a growing number of military vessels from different countries has led to fears of accidental clashes and miscalculations. But a code of unplanned encounters at sea that the U.S. and China observe has helped prevent misunderstandings.
"Not a day goes by ... we don't have an encounter at sea," Kacher said, but he added that "those engagements are professional."
Still, the new strategically located islands would give China more security leeway in the disputed waters and make it difficult for U.S. forces to assert sea control, Carl Thayer of the Australian Defence Force Academy said.
"China has excised the maritime heart out of Southeast Asia," Thayer said. "This is the new normal."
Associated Press writer Christopher Bodeen in Beijing contributed to this report.