South Korea Sunday declared an expanded air defence 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 defence 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 defence 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 neighbours and objections from key allies such as the United States.

"We will coordinate with related countries to fend off accidental military confrontations and to ensure the safety of airplanes," said South Korean defence ministry spokesman Kim Min-Seok.

"The new air defence zone is in line with international aviation rules and protocols," he said.

Kim said Seoul had notified its neighbours and related nations in advance about its new air zone -- the first revision to its air defence area for 62 years.

The new zone was expanded by about 66,480 square kilometres (25,670 square miles) -- or about two thirds of the size of the country -- in waters off its south coast, the defense ministry said.

There was no immediate comment from China or Japan on the South Korean move.

The US State Department spokesperson Jen Psaki confirmed that Seoul had consulted with Washington earlier, saying US officials "appreciate" the South's "efforts to pursue this action in a responsible... fashion" by notifying its neighbours in advance.

Tension has been high since the air zone declaration by China, which neighbours see as a push to assert its growing military might and territorial claims.

In addition to Ieodo China's ADIZ covers disputed Tokyo-controlled islands, known as the Senkakus in Japan and the Diaoyus in China, that have been at the centre of a simmering territorial row.

Both Tokyo and Seoul have rejected Beijing's demand that all aircraft traversing the Chinese zone file flight plans and ID details.

The US flew two US B-52 bombers through the area without complying, followed by similar moves by Japan and South Korea whose planes also entered the zone without notifying China.

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

Biden warned China against raising tension in the region, saying regional peace and stability were in its interests.

Biden, during talks with South Korean President Park Geun-Hye, also expressed "understanding" for Seoul's approach including the revision of its air zone, according to a senior US official.

Boo Hyung-wook, a researcher at the Korea Institute of Defense Analyses, said the latest dispute stems from China's desire to strengthen its claim over the Senkakus by extending its air defence zone.

"Since South Korea was so close to Japan, it was unavoidable (for China) to let some of its air zone overlap with Korea, which has led to all this trouble with Seoul," Boo said.

"It's really time for the three neighbours to sit together to avoid the worst case scenario," he said, adding however it was "highly unlikely" that the latest row would lead to an actual military clash.