TOKYO - Japan accused China of flying fighter jets “dangerously” close to two of its military planes over the East China Sea Wednesday, as bilateral tensions simmer over the countries’ territorial dispute.

Two Chinese SU-27 jets flew as close as 30 metres (100 feet) away from the Japanese defence aircraft at about 11am local time (0200 GMT), the defence ministry in Tokyo said. Defence Minister Itsunori Onodera told reporters his ministry had lodged a diplomatic complaint with China over the incident. It was the second time in less than three weeks that Tokyo accused Beijing of “dangerous” flights by Chinese fighter jets against Japanese military planes. The alleged incident occurred over the open seas near the disputed waters where China’s stated air defence identification zone overlaps with that of Japan.

The area is about 200-300 kilometres (125-190 miles) north of the Japanese-controlled Senkaku islands, which China also claims and calls the Diaoyus.

Defence Minister Onodera called the Chinese aircraft’s manoeuvres “extremely dangerous flights that could have led to an accident.” “We cannot allow this to happen,” he said, urging Beijing to preventing a recurrence by by establishing a hotline between their defence officials.

In an apparent tit-for-tat move, the Chinese defence ministry said on May 29 that two Japanese fighter planes came within 10 metres of a Chinese transport aircraft over the East China Sea in late November last year.

The territorial dispute flared in September 2012 when Tokyo nationalised some of the islands.

Chinese state-owned ships and aircraft, including coastguard vessels, have since approached the island group, sometimes venturing into its territorial waters and airspace, chased by Japanese coastguard patrols and prompting Tokyo to scramble fighter jets.

Fears of a military clash in the area have been heightened after China unilaterally declared last November the establishment of its air defence identification zone above the East China Sea, which overlaps a similar Japanese zone.

Meanwhile, Japan lashed out at China Wednesday for politicising a UN agency with a bid to register papers on its wartime misdeeds of sexual slavery and the Nanjing massacre in a global document trove.

Beijing said Tuesday it wanted the United Nations Educational, Scientific and Cultural Organisation (UNESCO) to include the information in the “Memory of the World” register, which is dedicated to preserving documentary heritage.

Chief Cabinet Secretary Yoshihide Suga denounced the plan, telling reporters Wednesday it was a backwards-looking move that would not help to resolve bitter disputes between the two countries.

“At a time when efforts are needed to improve Japan-China relations, it is extremely regrettable that China moved to make political use of the UNESCO forum and to unnecessarily play up the negative legacy of ties from a period of the past,” he said.

That came after Chinese foreign ministry spokeswoman Hua Chunying announced Beijing wanted the world to remember the sufferings Japan had inflicted.

“By applying for the inclusion of precious historical documents related to the Nanjing Massacre and Japan’s forced recruitment of the ‘comfort women’ in the register, China is to memorise the history,” she said.

It wanted to “treasure the peace, uphold the dignity of mankind and prevent behaviours against humanity, human rights and human beings from happening again,” she said.

In the 1937 “Rape of Nanjing”, China says 300,000 people were killed and thousands raped as Japanese troops rampaged through the city during their invasion of the Asian mainland.

No respected historian disputes that imperial troops were responsible for large-scale atrocities, but some in Japan and abroad say the Chinese death toll is inflated.

Japan’s system of sex slavery up to and during World War II, in which thousands of mainly-Korean “comfort women” were forced into military brothels continues to cause revulsion.

Numerous apologies have not dampened calls for Japan to properly atone for the practice, while equivocations from senior Japanese politicians - including Prime Minister Shinzo Abe - have exacerbated the impression that Tokyo wants the world to forget the horrific practice.

China’s bid to get the documents on the register - which includes the Magna Carta and Beethoven’s 9th Symphony - is the latest example of the way history continues to poison ties between Asia’s two largest economies.

Relations have become increasingly sour since Japan nationalised islands in the Tokyo-controlled Senkaku chain in the East China Sea.

Beijing says the islands, which it calls the Diaoyus, have belonged to China for hundreds of years, and their 1895 incorporation into Japan marked the opening shots of a half-century-long campaign to invade and subjugate Asia, culminating in World War II.

Critics in Japan and elsewhere say China uses history as a cudgel to beat Tokyo, largely for a domestic audience, despite its nearly seven-decade committment to pacifism.