BEIJING China's Foreign Ministry said on Thursday the government was investigating a complaint from Japan that a Chinese navy vessel aimed a type of radar normally used to aim weapons at a target at a Japanese navy ship in the East China Sea.
"The relevant Chinese departments are currently conducting an earnest, solemn investigation into these reports to verify them," ministry spokeswoman Hua Chunying told a daily news briefing.
The Chinese Defence Ministry has yet to comment on Japan's complaint.
Japanese Defence Minister Itsunori Onodera said this week that the incident, which he said occurred on January 30 but took time to confirm, could have become very dangerous very quickly.
Hua said that it was actually Japan that was provoking tension over a group of disputed, uninhabited islands, called Diaoyu by China and Senkaku by Japan and which are also claimed by Taiwan.
"The problem at present is not China showing strength, but Japan continuously sending its ships and aircraft into the waters and airspace around the Diaoyu Islands to carry out illegal activities, damaging and infringing upon China territorial sovereignty," she said.
"Recently, Japan has been intentionally stirring up a crisis and causing tensions, blackening China's image. This is diametrically the opposite of efforts to improve relations."
Onodera said on Thursday China's use of the radar could be seen a threat of military force under U.N. rules, but urged dialogue to prevent such incidents happening again.
The minister reiterated that there was a need to establish a communication channel to discuss maritime issues.
Japanese Prime Minister Shinzo Abe spoke in a similar vein, repeating that the incident was regrettable but stressing that maintaining dialogue with China was important.
Fears that cat-and-mouse encounters between aircraft and ships could lead to an accidental clash have given impetus to efforts to reduce the tension, including a possible summit between Abe and Chinese leader Xi Jinping, who takes over as head of state in March.
Despite the complaint over the radar, hopes have been rising for a thaw in ties between Asia's two biggest economies since relations soured significantly in September when Japan nationalized the isles.
The purchase from a private citizen was aimed at easing the long-running row but it triggered violent protests in China.
(Reporting by Ben Blanchard; Additional reporting by Antoni Slodkowski in TOKYO; Editing by Robert Birsel)