Philippine President Benigno Aquino said on Wednesday the concrete blocks found on a disputed shoal in the South China Sea are "very old", backtracking on Manila's earlier accusation that China was building new structures in the area.

In an embarrassing twist after foreign affairs and defense officials had accused China of preparing to build new structures on Scarborough Shoal, a group of rocks about 120 nautical miles off the coast of the main island of Luzon, Aquino said the blocks found within the shoal "are not a new phenomenon" and "some of them have barnacles attached to them."