TOKYO: Japan on Sunday accused China of "dangerous" manoeuvres above the disputed East China Sea after a Chinese fighter flew within roughly 30 metres (100 feet) of a Japanese military aircraft. A Japanese defence ministry spokesman said that a Chinese SU-27 jet on Saturday flew close by a Japanese OP-3C surveillance plane above the waters where the countries' air defence identification zones overlap. Another Chinese SU-27 fighter also flew close by a Japanese YS-11EB plane in the same airspace, the ministry said. One fighter jet flew about 50 metres and the other was as close as 30 metres to the Japanese planes, according to the spokesman. The incidents come as relations between Japan and China are strained amid a territorial dispute over Tokyo-controlled islands in the East China Sea. "They were dangerous acts that could lead to an accident," Japanese Defence Minister Itsunori Onodera told reporters on Sunday. "The Japanese crew reported that the fighters were flying with missiles, which raised the tension as they handled the situation. "I consider the (Chinese fighters) acted out of rule." Tokyo protested Beijing over the incidents through diplomatic channels, he said. The Chinese fighters did not enter the Japanese zone, according to the Asahi Shimbun daily. The two Japanese aircraft were monitoring a joint naval drill by China and Russia in the northern East China Sea near Japanese territorial waters, Kyodo News said, citing an unnamed government source. Chinese state-owned ships and aircraft have periodically approached the Senkaku islands, which China also claims and calls the Diaoyus, to demonstrate Beijing's territorial claims in the East China Sea. Beijing raised regional tensions in November by declaring an air defence identification zone covering the area, which overlaps a similar Japanese zone.