Beijing demanded on Monday that Tokyo explain reports that Japanese Prime Minister Shinzo Abe said Japan's security legislation is directed at China.
Japan's Gendai Business weekly reported on Monday that Abe said at a meal with high-ranking media figures earlier this month that Japan's "security policy bills are targeted at China in the South China Sea".
Abe was quoted as saying that Japan should exercise the right of collective self-defence and side with the United States against China in the South China Sea.
Gendai Business reported that the prime minister's office had warned media attending the meal not to report the remarks, so certain journalists at the meal who are worried about the legislation sent the information to the magazine and other media.
The reports drew a swift rebuke from Beijing. Foreign Ministry spokeswoman Hua Chunying said: "We have noticed the report. If it is confirmed true, we believe Japan should issue an explanation and clarification."
Hua said people should remain on "high alert" about the aims behind Japan's recent moves, including changing its security policies, revising its Constitution and expanding its armed forces, as well as creating tensions in the South China Sea, in which Japan has no territorial claims.
"We urge Japan to learn from the lessons of history, follow the path of peaceful development and act prudently on military and security affairs to avoid making the same mistakes," Hua said.
A survey released by Japan's Nikkei business daily on Monday found the proportion of voters opposed to Abe's administration rose to 40 per cent over doubts about the security policy. It is the highest ratio since Abe retook office in 2012.
Abe has vowed to enact legislation to implement a historic defence policy shift this summer. But 56 per cent of voters oppose his plan to end a self-imposed ban on exercising the right of collective self-defence, or militarily aiding a friendly country under attack. That could allow Japanese troops to fight abroad for the first time since Tokyo's defeat in World War II.
Eighty-one per cent of those polled said the government's explanation for the change has been insufficient.
Japan has vowed to join countries that have territorial disputes with China to contain Beijing.
Last week, Japan held a joint drill with the Philippines in the South China Sea and had its military patrol planes fly over areas claimed by China.
"Whether or not the report about Abe's remarks is true, it is apparent that Japan has moved on to join the US to contain China in the South China Sea," said Wang Ping, a researcher on Japanese studies with the Chinese Academy of Social Sciences.
As for Japan's domestic objection to security legislation, Wang said the bills violate Japan's postwar pacifist Constitution.
"So that has drawn opposition from ordinary people, law scholars, opposition parties and all the forces cherishing peace," she said.