Tokyo (AFP) - Japan on Sunday accused China of "dangerous" manoeuvres above disputed areas of the East China Sea, saying a Chinese fighter flew within roughly 30 metres (100 feet) of a Japanese military aircraft.
A defence ministry spokesman said a Chinese Su-27 jet on Saturday flew close to 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 to a Japanese YS-11EB plane in the same airspace, the ministry said.
One fighter jet approached to within about 50 metres and the other was as close as 30 metres to the Japanese planes, according to the spokesman.
Relations between Japan and China are strained by a territorial dispute over Tokyo-controlled islands 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.
"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."
Tokyo protested to Beijing over the incident 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.
Chinese state-owned ships and aircraft have periodically approached the Senkaku islands, which China also claims and calls the Diaoyus, to assert Beijing's claim to them.
China's defence ministry said two Japanese planes entered China's air defence identification zone on Saturday, "interfering with joint naval exercises between China and Russia" for which a "no fly" notice had been issued.
Chinese aircraft were scrambled to "identify and take protective measures" against the Japanese planes, the ministry said in a statement on its website.
China has made representations to Japan asking it to "respect the legitimate rights of the Chinese and Russian navy", it said.
China and Russia started joint naval exercises on Tuesday as their leaders promised to strengthen relations in the face of international criticism over their territorial disputes.
The exercises ended on Sunday.