The zone covers territory claimed by China, Japan, Taiwan and South Korea.
China said last week that all aircraft crossing through the zone must file flight plans and identify themselves or face “defensive emergency measures”.
The US, Japan and South Korea say they have since defied the ruling and flown military aircraft in the area.
The air defence identification zone (ADIZ) covers a vast area of the East China Sea and includes a group of islands which are claimed by Japan, China and Taiwan.
South Korea claims ownership of a submerged rock, known as Ieodo, within the zone.
The establishment of the ADIZ has caused widespread anger, with the US calling it a “destabilising attempt to alter the status quo in the region”.
On Thursday, China had announced it was deploying warplanes in the area as a “defensive measure” and to carry out routine surveillance.
Then on Friday, Air Force spokesman Col Shen Jinke said Chinese warplanes had been scrambled that morning to identify two US surveillance aircraft and 10 Japanese planes – including early warning aircraft, surveillance aircraft and fighter jets – crossing through the ADIZ, state media reports.
Col Jinke made no reference to whether any further action was taken by any of the aircraft.
Earlier, Foreign Ministry spokesman Qin Gang said China had a right to patrol the region and that it the ADIZ was not aimed at any specific country.
“It’s absolutely a measure designated to exercise the right of defence effectively,” he told a regular briefing.
“If some worry has emerged about the situation, it’s agitated by some individual countries.”
If maritime disputes existed, China wanted to solve them through “peaceful means via friendly negotiation,” state news agency Xinhua quoted him as saying.
Japanese Prime Minister Shinzo Abe said on Friday that Japan would respond “firmly but in a calm manner” to China’s move, the Kyodo news agency reports.
Foreign Minister Fumio Kushida said the issue would be discussed with US Vice-President Joe Biden, who is due to begin a three-day visit to Japan on Monday.
The disputed group islands in the zone – known as Senkaku in Japan and Diaoyu in Chinese – are uninhabited, but have been the subject of rising tensions in recent years.
They are controlled by Japan, and were under private ownership until the Japanese state bought them in 2012, angering China.
South Korea has also complained to China that the ADIZ overlaps its own similar defence zone, and encompasses the Ieodo rock, but Beijing has said it will not redraw the lines.
There are fears that the increasing tension and militarisation of the region could escalate into an unplanned military incident.