Manila  - Philippine President Gloria Macapagal Arroyo has signed into law a bill defining the country's territorial boundaries and laying claim to disputed areas in the South China Sea, a top aide said Wednesday.

Presidential Executive Secretary Eduardo Ermita said Arroyo signed the Baselines Law on Tuesday despite a strong protest by China over the measure.

"We are sending the message to the whole world that we are affirming our national sovereignty," Ermita said. "We are affirming our national interest."

Aside from marking the Philippines' maritime boundaries, the Baselines Law also identified "regime of islands under the Republic of the Philippines" or areas over which the country exercises "sovereignty and jurisdiction."

These areas include the Scarborough Shoal - a group of islets, atolls and reefs claimed by China - and the Kalayaan Islands, a part of the Spratlys, which are claimed in whole or in part by China, Brunei, Malaysia, Taiwan and Vietnam.

The Spratlys straddle key shipping lanes in the South China Sea and are believed to be rich in oil, marine and mineral resources.

In November 2002, the claimant countries signed an agreement to refrain from taking steps that could trigger conflict among them and to hold consultations on possible joint ventures.

In the past, the Philippines has clashed with China and Vietnam over various incidents in the Spratlys, including the shooting of a Philippine plane by Vietnamese troops and the construction of concrete buildings by China. (dpa)