The Philippine government has recently accused China of putting posts and a buoy in Filipino- claimed waters, but Tonsay said the Navy had not been able to determine who placed the wooden posts that it removed in May.
“They did not have a ‘Made in China’ label or anything,” Tonsay said, adding the posts had only numbers on them.
The markers were on Boxall Reef in the Spratly Islands, and in the nearby Amy Douglas Bank and Reed Bank, all of which are in waters of the South China Sea claimed by the Philippines and China.
Aside from the Philippines and China, Brunei, Malaysia, Taiwan and Vietnam have overlapping territorial claims to strategically vital and reputedly resource-rich areas of the South China Sea.
Tensions over the long-running dispute have escalated in recent months amid assertions by the Philippines and Vietnam that China has become increasingly aggressive in staking its claims to the areas.
The Philippines this month accused China of undermining peace and stability in Asia by allegedly sending naval vessels near Reed Bank to intimidate rival claimants, and of installing posts and a buoy in nearby areas.
The Philippines also protested over incidents in February to May, accusing the Chinese navy of opening fire on Filipino fishermen and intimidating a Philippine oil exploration ship.
Raising tensions further, President Aquino said on Tuesday that his country needed help from longtime ally the United States in its dispute with China. Chinese embassy spokespersons in Manila did not answer telephone calls on Wednesday about the foreign markers.
A spokesperson at the Department of Foreign Affairs declined to comment on the naval action.