Beijing has condemned Japanese Prime Minister Shinzo Abe for "maliciously slandering" its air defence zone in an escalating war of words.
Abe told a news conference on Saturday that China's recent announcement of the air defence identification zone over the disputed Diaoyu, or Senkaku, islands in the East China Sea is "unjustly violating the freedom of aviation over the high seas".
He demanded that Beijing rescind it.
But Chinese Foreign Ministry spokesman Hong Lei defended the zone, which has triggered protests from Japan, South Korea and the United States.
"We express strong dissatisfaction with Japan's leader using an international occasion to maliciously slander China," Hong said in a statement on the ministry website.
"The Diaoyus are an inherent territory of China. Japan's seizure and occupation of the islands are illegal and invalid," Hong said. He added that the zone is in line with international laws and practices and does not affect aviation freedom.
He continued: "The Chinese side took necessary measures to safeguard its sovereignty and territorial integrity.
"This is totally legitimate and irreproachable. Japan's attempt to play tricks with concept ... and mislead world opinion is doomed to failure." China's air defence zone and its territorial claims in the South China Sea have raised concerns that a minor incident in the disputed seas could quickly escalate.
China and several Asean nations have competing territorial claims in the energy-rich South China Sea.
Abe and leaders of the Association of Southeast Asian Nations agreed at a summit in Tokyo on Saturday on the need for freedom of the high seas and skies and called for the peaceful resolution of disputes.
The statement did not criticise China's air zone.
Many Asean members have deep economic ties with China.
Sino-Japanese tensions have risen over the past year in a long-running dispute over the Japanese-controlled Diaoyu Islands, which Japan calls the Senkakus.
Both countries have scrambled aircraft and conducted naval patrols in the area.
Taiwan also claims sovereignty over the islands.