Chinese state-run media Friday identified Japan as Beijing's "prime target" in its newly declared air defence zone, calling for "timely countermeasures without hesitation" if Tokyo defies it.

However, other countries which have sent military aircraft into the air defence identification zone (ADIZ), including the United States and South Korea, should be largely ignored, the Global Times said.

"We should carry out timely countermeasures without hesitation against Japan when it challenges China's newly declared ADIZ," the paper, which is close to China's ruling Communist party, said in an editorial.

China's ADIZ which was declared on Saturday requires aircraft to provide their flight plan, declare their nationality and maintain two-way radio communication, or face "defensive emergency measures".

The zone overlaps those declared by Japan and South Korea, and includes airspace over East China Sea islands disputed with Tokyo.

The move triggered US and Japanese accusations of provocation, and criticism from South Korea and Australia.

Tokyo and Seoul said Thursday they had defied the zone with military overflights, showing a united front after Washington sent B-52 bombers through the airspace.

China's military sent several fighter jets and an early warning aircraft into the zone on Thursday, the official Xinhua news agency reported, after first patrolling it on Saturday.

Shen Jinke, spokesman for the People's Liberation Army (PLA) Air Force, said the move was "a defensive measure and in line with international common practices".

The Global Times editorial, headlined "Japan prime target of ADIZ tussle", said: "If the US does not go too far, we will not target it in safeguarding our air defence zone.

"What we should do at present is firmly counter provocative actions from Japan."

The paper, which often takes a nationalistic tone, added that Australia can be "ignored" as the two countries have no major grievances, and that Beijing has "no need to change its actions" towards Seoul, given that South Korea has its own "tensions" with Japan.

Officials in China have previously accused the US and Japan -- which both have ADIZs -- of double standards, saying the real provocateur is Tokyo.