The two zones will now both include a rock claimed by both countries and controlled by South Korea.
The defence ministry said it would co-ordinate with "related countries".

China announced a new Air Defence Identification Zone (ADIZ) last month, in a move that raised regional tensions.

Both countries' zones will cover the airspace above a rock called Ieodo by South Korea and Suyan by China, which is claimed by both countries.

As well as Ieodo rock, South Korea's Defence Ministry also said the new military air defence zone would cover the airspace above Marado and
Hongdo islands controlled by Seoul in waters south of the peninsula.

The new parameters are a direct challenge to China's own air defence zone, which covers part of the same area,
says the BBC's Lucy Williamson in Seoul.

South Korea said its zone would take effect on 15 December, and that neighbouring countries had already been notified of the change.

The government would continue to consult with neighbouring countries to stop accidental military clashes, it said.

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