South Korea Sunday declared an expanded air defense zone that overlaps with one announced by China and covers a submerged rock disputed by the two countries, as tensions rise over competing territorial claims.

South Korea Sunday declared an expanded air defense zone that overlaps with one announced by China and covers a submerged rock disputed by the two countries, as tensions rise over competing territorial claims.

The defense ministry said its new zone, which will take effect on December 15, would cover Ieodo -- a rock in waters off its south coast which China calls Suyan.

The airspace above the Seoul-controlled rock -- long a source of tension between South Korea and China -- is also covered by Chinese and Japanese air defense zones.

China heightened tensions last month when it unilaterally declared an Air Defence Identification Zone (ADIZ) in the East China Sea, in which foreign planes are supposed to file flight plans with Beijing.

The zone -- which encompasses some areas currently controlled by South Korea or Japan -- has drawn intense protests from the two neighbors and objections from key allies such as the United States.

South Korean defense ministry spokesman Kim Min-Seok said Seoul had notified its neighbors and related nations in advance about its new air zone -- the first revision to its air defense area for 62 years.

The new zone was expanded by about 66,480 square kilometers or about two thirds of the size of the country -- in waters off its south coast, the defense ministry said.

The latest tension over the air zone overshadowed the visit last week by US Vice President Joe Biden to the three nations.

Biden, during talks with South Korean President Park Geun-Hye, also expressed "understanding" for Seoul's approach including the revision of its air zone, warning China against raising tension in the region, saying regional peace and stability were in its interests.