Beijing - China and Japan engaged on Friday in a fresh round of invective over military movements near a disputed group of uninhabited islands, fuelling tensions that for months have bedevilled relations between the two major Asian powers.
China's defence ministry rejected a Japanese allegation that a naval vessel had aimed a weapons-targeting radar at a Japanese military ship in the East China Sea, its first comment on the week-old incident.
It said Japan's intrusive tracking of Chinese vessels was the "root cause" of the renewed tension.
A Japanese official on Friday dismissed the Chinese explanation for the 30 January incident.
He said Beijing's actions could precipitate a dangerous situation in waters around the islets, known as Diaoyu in China and Senkaku in Japan, believed to be rich in oil and gas.
His comments came a day after Japan said two Russian fighter jets briefly entered its air space near other, long-disputed islands, prompting Japan to scramble combat fighters. Russia denied the charge.
China's defence ministry, in a statement issued late on Thursday, said Japan's remarks "do not match the facts".
The Chinese ship's radar, it said, had maintained regular alerting operations and "did not use fire control radar".
The ministry said the Chinese ship was tracked by a Japanese destroyer during routine training exercises.
Fire control radar pinpoints the location of a target for missiles or shells and its use can be considered a step short of actual firing.
Japan, it said, had recently "made irresponsible remarks that hyped up the so-called 'China threat', recklessly created tension and misled international public opinion.
"... In recent years, Japanese warships and aeroplanes have often conducted long periods of close-range tracking and surveillance of China's naval ships and aeroplanes. This is the root cause of air and maritime security issues between China and Japan."
In Tokyo, Japan's Chief Cabinet Secretary Yoshihide Suga told a news conference on Friday: "We cannot accept China's explanation."
Japan's allegations, he said, had been "a result of our defence ministry's careful and detailed analysis. We urge China to take sincere measures to prevent dangerous actions which could cause a contingency situation."
Japanese Defence Minister Itsunori Onodera said this week that the incident could have become very dangerous very quickly, and that use of the radar could be seen as a threat of military force under UN rules.
Hopes have been rising in recent weeks for a thaw in ties after months of tension, sparked, in part, by Japan's nationalisation of three of the privately owned islets last September.
Fears that encounters between aircraft and ships could degenerate into an accidental clash have given impetus to efforts to improve links, including a possible summit between Abe and Chinese leader Xi Jinping, who takes over as head of state in March.