TOKYO (REUTERS) - Japan and China on Sunday accused each other's air forces of dangerous behaviour over the East China Sea, with Japan saying Chinese aircraft had come within a few dozen metres of its warplanes.

Japan's defence minister accused Beijing of going "over the top" in its approach to disputed territory. China's defence ministry said Japanese planes had carried out "dangerous"actions during its joint maritime exercises with Russia.

Tensions have been running high between China and its neighbours over Beijing's assertive stance on claiming land and sea territory.

Japan's defence ministry said Chinese SU-27 fighters came as close as 50 metres to a Japanese OP-3C surveillance plane near disputed islets on Saturday and within 30 metres of a YS-11EB electronic intelligence aircraft.

"Closing in while flying normally over the high seas is impossible," Defence Minister Itsunori Onodera told reporters in comments broadcast on TV Asahi. "This is a close encounter that is outright over the top." Onodera said Japan conveyed its concerns to the Chinese side through diplomatic channels. He also said the Chinese planes were carrying missiles.

A ministry official said it was the closest Chinese warplanes had come to aircraft of Japan's Self-Defence Force.

China's defence ministry said jets were scrambled in the East China Sea on Saturday after Japanese aircraft entered its air defence zone during maritime exercises with Russia.

The ministry said the Japanese aircraft had entered the zone despite "no fly" notices being issued ahead of the exercises. China declared its air defence zone last year despite protests by Japan and the United States. "Japanese military planes intruded on the exercise's airspace without permission and carried out dangerous actions, in a serious violation of international laws and standards, which could have easily caused a misunderstanding and even led to a mid-air accident," the statement said.

China had proposed urgent talks, it said, and demanded that Japan "respect the lawful rights of China's and Russia's navies ... and stop all reconnaissance and interference activities. Otherwise Japan will bear any and all consequences from this".

China lays claim to Japanese-administered islets in the East China Sea, known as Senkaku in Japanese and Diaoyu in Chinese. It is also pressing its claim to almost all the South China Sea, brushing aside claims by several southeast Asian states.

China's proclamation last November of an air defence zone covering disputed islands and areas in the South China Sea has raised concerns that a minor incident could quickly escalate.

Sino-Japanese ties have long been strained by allegations in China that Japan has not properly atoned for its wartime aggression and by the spat over the uninhabited islands.

Japan scrambled fighter jets against Chinese planes 415 times in the year ended in March, up 36 percent on the year, while in waters near the disputed islands, patrol ships from both countries have been playing cat-and-mouse, raising fears of an accidental clash.

Japanese land, sea and air forces joined last week to simulate the recapture of a remote island, underscoring Tokyo's concerns about the security of the islets.

Tensions between China and its neighbours have also risen sharply in the South China Sea in recent weeks, following the deployment of a Chinese oil rig in waters also claimed by Vietnam. The deployment sparked anti-Chinese riots in Vietnam.

The Philippine foreign ministry this month accused China of reclaiming land on a disputed reef in the South China Sea and said it appeared to be building an airstrip.