1 of 6
Aaron Favila, Associated Press
A Filipino activist raises a slogan during a rally in front of the U.S. embassy in Manila, Philippines on Monday, April 20, 2015. The group is protesting against a joint U.S.-Philippines military exercise dubbed "Balikatan 2015" where troops from both countries take part in an annual drill that focuses on regional security, terrorism, disaster preparedness and inter-operability.

MANILA, Philippines — More than 11,500 American and Filipino military personnel launched one of their largest annual combat readiness exercises Monday amid growing alarm over massive land reclamations by China in disputed South China Sea territories.

Philippine military officials said the "Balikatan," or shoulder-to-shoulder, maneuvers, which involve more than 90 aircraft and ships, were not directed at China. But the venue of some of the war games in waters facing the disputed region and a focus on territorial defense appear to link the exercises to the long-simmering conflict.

Shortly before overseeing the start of the military exercises, Philippine military chief Gen. Gregorio Pio Catapang Jr. held a separate news conference to release surveillance photos showing Chinese reclamations in eight previously submerged reefs in the disputed Spratly Islands, saying Beijing's actions increase the risk of an accidental confrontation.

"We have compelling reasons to raise our voice to tell the whole world the adverse effects of China's aggressiveness that has created tensions not only among the countries who have overlapping claims in the area," Catapang said.

Once completed, the artificial islands could be transformed into offshore military bases with airstrips and maritime patrol hubs that could threaten the freedom of navigation in that section of the South China Sea, with busy oil and commercial cargo lanes, he said.

Catapang said some of the reclamation projects were several kilometers (miles) from a Philippine-occupied island and a reef, raising the possibility that Chinese military patrols could cut off Manila's access, along with that of Filipino fishermen, to those areas.

Philippine government agencies were meeting to determine how to respond to the situation, Catapang said, adding the country wants a peaceful resolution based on international laws.

Chinese officials have defended the land reclamations by saying it is Beijing's territory, adding the reclamations were for public service use and to support fishermen.

But the Philippine military has said the massive scale of the reclamations and the emergence of runway-like facilities raise the possibility they could be for military use to reinforce China's extensive territorial claims.

The chain of Spratly islands, reefs and atolls where most of the Chinese land reclamations have been detected, has long been contested by China, the Philippines, Taiwan, Malaysia, Vietnam and Brunei. Aside from possible oil and natural gas resources, the vast region also straddles busy sea lanes and teems with rich fishing grounds.