Foreign Minister Fumio Kishida said Sunday that Japan does not acknowledge China's establishment of an air defense identification zone over the Japan-controlled Senkaku islets group.
"It was a one-sided action and cannot be allowed. It's also expected to trigger unpredictable events," he told reporters in Fuchu, western Tokyo, a day after Beijing set up the zone.
The defense zone demarcated by China includes airspace over the Japan-controlled Senkaku Islands. The islands are claimed by China and Taiwan, which call them Diaoyu and Tiaoyutai, respectively.
The Japanese Defense Ministry said Saturday two Chinese planes entered Japan's air defense identification zone, prompting the Air Self-Defense Force to scramble fighter aircraft.
Although Japan lodged a strong protest with China on Saturday over the zone's establishment, Kishida said Tokyo is considering making a protest at a higher level apparently including one by himself.
Kishida also welcomed the United States having conveyed its "strong concerns" to China over the zone issue.