The long-running row over the islands, known as the Senkaku in Japan and the Diaoyu in China, has in recent months escalated to the point where both sides have scrambled fighter jets while patrol ships shadow each other.

Chinese officials were not available for comment on Japan’s complaint about the radar, but a Chinese spokeswoman earlier urged Japan to stop what she called provocation.

“We believe that what is most urgent is for Japan to stop provocative actions like regularly sending in ships and aircraft into the waters around the Diaoyu Islands  and seek, via talks with China, an effective way to appropriately control and resolve this issue,” Foreign Ministry spokeswoman Hua Chunying told a news conference when asked about Chinese ships operating in waters near the disputed islands.

IN SEARCH OF A SUMMIT

Fears the cat-and-mouse encounters between aircraft or ships will cause an accidental clash have given impetus to efforts to reduce the tension, including the possible summit between Japanese Prime Minister Shinzo Abe and Chinese leader Xi Jinping, who formally takes over as head of state in March.

Abe’s junior coalition partner, Natsuo Yamaguchi, who heads the small New Komeito party, said a summit could take place as early as April if both sides tried hard to smooth the path.

Yamaguchi met Xi last month to deliver a letter from Abe, who took office in December after his party won an election. Abe, a security hawk who has vowed to stand firm in the islands row, earned a track record of fixing frayed ties with China during his previous 2006-2007 term as prime minister.

“There are two big opportunities,” Yamaguchi told Reuters in an interview, referring to chances for a summit. “One would be when the passage of the budget is assured in Japan.”