Media playback is unsupported on your device Media caption The BBC's Rupert Wingfield-Hayes tried to reach the islands in November 2012

Japan says it may release evidence to prove a Chinese naval frigate locked its fire-control radar onto a Japanese ship near disputed islands.

Tokyo said it might release the data after Beijing rejected accusations it had targeted the destroyer last month.

China insists its ship was only using ordinary surveillance radar.

The incident would be the closest the two countries have come to exchanging fire in the reignited dispute over the islands in the East China Sea.

The situation is certainly the most serious for Sino-Japanese relations in the post-war period in terms of the risk of militarised conflict. The two sides have had periodic deteriorations in bilateral ties before and usually found a way to settle if not resolve differences. There are mechanisms to defuse tensions somewhat but there is also perhaps a lack of leadership on both sides necessary to really focus on dealing with the problems. We are seeing the coincidence of two regimes in China and Japan which are facing crises of legitimacy and a temptation to turn to issues of nationalism to compensate. The problems of the legitimacy of the Chinese Communist Party in trying to maintain one party rule in the face of pluralist pressures are well known. Japan is a democracy so does not face quite the same pressures, but there is a similar sense of the bankruptcy of the legitimacy and competency of the governing elites, and all of this is set against a difficult economic climate. Viewpoints: How serious are China-Japan tensions?

The two nations are embroiled in a bitter territorial row over the islands, known as Senkaku in Japan and Diaoyu in China. Japan controls the islands, which are also claimed by Taiwan.

"The government is considering the extent of what can be disclosed," Kyodo news agency quoted Japanese Defence Minister Itsunori Onodera as saying.

On Friday, Prime Minister Shinzo Abe called on Beijing to acknowledge the 30 January incident and apologise.

Earlier this week, Mr Onodera said a Japanese military helicopter was also targeted with a similar type of radar by another Chinese frigate on 19 January.

But China's Defence Ministry has denied the Japanese allegations saying they "were against the facts" and urging Japan to "stop stirring up tension in the East China Sea".

The Chinese Defence Ministry, in its statement, said that in each incident, the Chinese vessel "kept normal observation and alert, and fire control radar was not used".

"China hopes that Japan take effective measures to stop stirring up tension in the East China Sea and making irresponsible remarks," it said.

Since the row over the islands flared up again last September, Chinese vessels have been sailing in and out of what Japan says are its territorial waters around the islands, prompting warnings from Tokyo.