China on Thursday sent several fighter jets and an early warning aircraft to its newly declared air defence zone in the East China Sea as a "defensive measure" after Japan and South Korea said their military planes flew through the area in defiance of Beijing's unilateral move.
Colonel Shen Jinke said several fighter jets and an early warning aircraft had been deployed to carry out routine patrols as "a defensive measure and in line with international common practices," state-run Xinhua news agency reported.
Shen said the country's air force would remain on high alert and would take measures to deal with all air threats to protect national security.
The Air Defence Identification Zone zone, announced by China last week, covers territory claimed by China, Japan, Taiwan and South Korea.
China has said all planes transiting the zone must file flight plans and identify themselves, or face "defensive emergency measures".
But Japan, South Korea and the US have all since flown military aircraft through the area.
Japanese aircraft had conducted routine "surveillance activity" over the ADIZ, a Japanese government spokesman said in Tokyo.
South Korea had also conducted a flight, the South Korean defence ministry said in Seoul.
A day earlier two giant US Stratofortress bombers flew through the AIDZ that China unilaterally declared.
The controversial zone includes disputed islands claimed by China, which calls them as the Diaoyus, but controlled by Japan, which terms them as the Senkakus.
Japanese officials did not specify when the flights happened, but confirmed the surveillance activity.
"Even since China has created this airspace defence zone, we have continued our surveillance activities as before in the East China Sea, including in the zone," Japan's government spokesman, Yoshihide Suga, said.
"We are not going to change this (activity) out of consideration to China," he said.
Under fire from the US and other countries over the ADIZ, Chinese Defence Ministry said it will consider to revoke the zone if Japan which has a similar defence zone withdraws it.
"Should the decision be retracted, we ask the Japanese side to revoke its Air Defence Identification Zone first, we will then consider their demand 44 years later," Defence Ministry spokesman Yang Yujun told reporters.
His comments came in response to Japanese Prime minister Shinzo Abe's call for China to withdraw the zone.