TOKYO - Japanese Prime Minister Shinzo Abe said Monday that Japan is seriously concerned over the air defense identification zone China announced to set up in the East China Sea on Saturday.

Abe made the remark at a session of a Diet committee, following the words made by Japan's Foreign Ministry on Sunday that Japan can not accept the fact that the zone covers the Diaoyu Islands.

China's foreign ministry spokesman Qin Gang said Sunday that China "firmly opposes" Japan's remarks on the Diaoyu Islands included in the identification zone, adding China's move conform to the Charter of the United Nations and international laws and practices and are thoroughly legitimate.

Qin said the remarks by the Japanese side are "irresponsible" and "groundless and utterly wrong."

The spokesman reiterated that the Diaoyu Islands and its surrounding islets are an inherent part of China's territory, and the country's determination and volition to safeguard its sovereignty over the islands are "unwavering."

China's Ministry of National Defense on Saturday issued an announcement to establish an Air Defense Identification Zone over the East China Sea.