The US expressed concern about China’s “unilateral action” and Japan said the East China Sea Air Defence Identification Zone, which came into effect on Saturday, was “totally unacceptable”.
Beijing has also issued a set of rules for the zone, saying all aircraft must notify Chinese authorities and are subject to emergency military measures if they do not identify themselves or obey orders. It said it would “identify, monitor, control and react” to any air threats or unidentified flying objects coming from the sea.
In Tokyo, Junichi Ihara, head of the Foreign Ministry’s Asian and Oceanian Affairs Bureau, protested by phone to China’s acting ambassador to Japan, Han Zhiqiang, saying the zone was “totally unacceptable”.
Mr Ihara also criticised China for “one-sidedly” setting up the zone and escalating bilateral tensions over the islands.
Both Beijing and Tokyo claim the islets, called Diaoyu in Chinese and Senkaku in Japanese. Protests erupted throughout China last year over the Japanese government’s purchase of the islands from private ownership.
China said the zone was in line with the practice of other nations that have similar zones to protect their coasts. The new zone overlaps with Japan’s existing zone, which also includes the disputed islands.
“This is a necessary measure taken by China in exercising its self-defence right,” Defence Ministry spokesman Yang Yujun said on the ministry’s website. “It is not directed against any specific country or target. It does not affect the freedom of overflight in the related airspace.”
US secretary of state John Kerry and defence secretary Chuck Hagel issued separate statements that said America was “deeply concerned” about the zone.
“This unilateral action constitutes an attempt to change the status quo in the East China Sea,” Mr Kerry said. “Escalatory action will only increase tensions in the region.”