China has condemned Shinzo Abe, the Japanese prime minister, for "maliciously slandering" its self-proclaimed air defence zone, ratcheting up the war of words between the neighbours over Beijing's annexation of the skies over a group of disputed islands.

Abe told a news conference that China's recent announcement of the air defence identification zone over disputed islands in the East China Sea was "unjustly violating the freedom of aviation over the high seas" and demanded Beijing rescind it. In the most bitter remarks so far in the dispute, the Chinese foreign ministry spokesman Hong Lei defended the zone, which has triggered protests from Japan, the United States and South Korea. "We express strong dissatisfaction with Japan's leader using an international occasion to maliciously slander China," Hong said in a statement seen on the ministry website on Sunday. The islands are claimed by Beijing as the Diaoyus and by Tokyo as the Senkakus. "The Diaoyus are an inherent territory of China. Japan's seizure and occupation of the islands are illegal and invalid," Hong said, arguing that the air zone was in line with international laws and practices, and did not affect aviation freedom. "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 of an escalation in the area. On Saturday the US navy said one of its warships monitoring a Chinese aircraft carrier was nearly hit by another Chinese military vessel and had to take evasive action.

China and several nations that are members of the Asean group have competing territorial claims in the energy-rich South China Sea. Abe and leaders of the Association of South-east Asian Nations agreed at a summit in Tokyo on Saturday for 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 islands in the East China Sea. Both countries have scrambled aircraft and conducted naval patrols in the area.