China has rejected claims from Japan that Chinese warships locked weapons guidance radar systems onto a Japanese destroyer and naval helicopter.
The defence ministry in Beijing said on Friday the accusations were not factual and accused Japan of fabricating reports to smear China. It urged Japan to "stop stirring up tension in the East China Sea".
Japan said the explanation did not match the facts.
The two nations are embroiled in a territorial dispute over the East China Sea islands, which are called Senkaku in Japan and Diaoyu in China. Japan controls the islands, which are also claimed by Taiwan.
Since September 2012, Chinese vessels have been sailing in and around the islands, prompting warnings from Tokyo.
Defence Minister Itsunori Onodera said on Tuesday a Chinese navy frigate close to the islands locked its weapon-targeting radar on a Japanese navy ship on 30 January.
He said a Japanese military helicopter was also targeted with a similar type of radar by another Chinese frigate on 19 January.