MANILA. Taiwanese leader Chen Shui-Bian landed on Ligao Island of the disputed Kalayaan group of islands (also known as Spratlys) around yesterday noon, Department of Foreign Affairs spokesman Claro Cristobal said.

And Foreign Affairs Secretary Alberto Romulo immediately protested it, calling it "irresponsible political posturing."

The landing is expected to cause tension among all the claimants.

This group of islands on South China Sea is claimed by the Philippines, Vietnam, China, Malaysia, Brunei, and Taiwan. The waters around the islands are believed to contain substantial petroleum reserves.

"It is lamentable that Taiwanese leader Chen Shui-bian pushed through with his plan to land on Ligao Island," Romulo said in a statement e-mailed to media outfits.

Romulo called this reported development a cause for "serious concern."

"It is unfortunate that Taiwan is resorting to what may be considered as irresponsible political posturing that could be of no possible advantage to the peace-loving Taiwanese people," he added.

Romulo said this Taiwanese action works against the joint efforts by all claimant countries to achieve peace and stability in the region.

These efforts are expressed in the Declaration on the Conduct of Parties in the South China Sea.

"The Philippines therefore urges all parties concerned to exercise prudence, self-restraint and use diplomacy as the tool to settle disputes in keeping with the spirit of the [Declaration on the Conduct]," Romulo said.

Cristobal said the landing was confirmed. "It might have been a land-and-run," he said.

Chen, whose Democratic Progressive Party was badly beaten in parliamentary elections January 12, made public his plan to visit the islands early this year. The visit is meant to assert Taiwan's claim before presidential elections in March.

Taiwanese media have reported that the trip was aimed at drumming up support for Frank Hsieh, the candidate for Chen's independence-leaning ruling Democratic Progressive Party in the March 22 presidential election.

Taiwan's defense ministry reportedly began building a 1,150-meter-long (3,800-feet) runway in the fortified Taiping islet in mid-2006, despite opposition by Vietnam. The project is nearly complete.