TOKYO - The Philippines on Thursday warned that territorial rows in Asia are "causing considerable tension that could lead to conflict" as several countries face off with China over island claims.

Philippine secretary of foreign affairs Albert del Rosario, speaking at a Tokyo business conference, said China's "nine-dash line claim encompassing almost the entire South China Sea" is "excessive."

"In addition to the South China Sea, we have in Northeast Asia, home to Asia's biggest economic powerhouses, several disputes that have adversely affected relations between and among Japan, China and the Republic of Korea.

"The competing territorial and maritime disputes are causing considerable tension that could lead to conflict," he warned.

China is believed to be boosting its naval capability in the Pacific and has been criticised by neighbours for what is seen as an increasingly aggressive stance in the region, particularly in its multiple territorial disputes.

Chinese maritime surveillance vessels have been frequently spotted in the 12-nautical-mile zone off the Tokyo-controlled Senkaku islands, which China calls the Diaoyus, in the East China Sea since Tokyo nationalised three of the outcrops in September.

China says it has sovereign rights over nearly all of the South China Sea, even waters far away from its main landmass and approaching the coasts of Southeast Asian countries.

The Philippines, Vietnam, Malaysia, Brunei and Taiwan also claim parts of the sea, and the area has for decades been regarded as a potential trigger for major military conflict in the region.

All claimants, except Brunei, have troops stationed on various islands and atolls in the Spratlys - the biggest archipelago in the sea - to assert their claims.