China's announcement yesterday that it had established an Air Defence Identification Zone in the East China Sea that includes the disputed Diaoyu Islands, known as the Senkakus in Japan, would greatly raise tensions and the risk of armed conflict, experts from both nations warned. The PLA said the zone, part of which overlaps Japan's ADIZ, became effective at 10am. Hours later, Beijing's new air force spokesman Colonel Shen Jinke said China had sent two large surveillance aircraft "to conduct the first patrol mission" in the new zone, escorted by an early-warning airplane and other multi-purpose jets. All aircraft entering the ADIZ would have to provide their flight plans, nationalities and maintain two-way radio contact allowing them to "respond in a timely and accurate manner to the identification inquiries" from Chinese authorities. Civil aviation would not be affected. Japan's foreign ministry yesterday lodged a "serious protest" to China, saying such a move was "extremely dangerous" and "could trigger unpredictable events", according to Junichi Ihara, chief of the ministry's Asian and Oceania Affairs Bureau. Taiwan, which also claims sovereignty over the disputed islands, expressed regrets. Although the Chinese defence ministry claimed the zone was not targeting any specific country, Xu Guangyu , a retired PLA general, said China was only "exercising its self-defence rights" in response to Japan's expansion of its ADIZ since the early 1970s and moves to limit China's rights to fly in the region. Experts warned that tension in the region would inevitably rise, especially because of the overlapping of the zones. Mainland-based Sino Japanese expert Liu Jiangyong said the chance of miscalculations would increase. "The air space above the tiny Diaoyus is so small that it is possible for high-speed fighter jets to crash into each other," Liu said. Jun Okumura, a visiting scholar at the Meiji Institute for Global Affairs, said: "I fully expect that the next time a Chinese aircraft flies into Japanese air space, Japanese fighters will be scrambled, there will be a war of words in the air and there could very well be shots fired, although I expect they would not be threatening shots. "I do not think either side will want to get into anything more serious, but these changes do now mean there is a far more serious likelihood of miscalculation," Okumura added. He pointed to an incident in 2001 in which a US Navy Orion EP-3 surveillance aircraft collided with a Chinese fighter over Hainan Island.