China has expressed its "strong opposition" to Japan's latest defense white paper, saying it has ulterior motives to play up a "China threat theory".

The Defense Ministry on Thursday joined the Foreign Ministry in condemning Tokyo's defense report, which voiced concern over China's military modernization and recent maritime activity.

"China unswervingly adheres to the path of peaceful development, sticks to the policy of building friendships and partnerships with neighboring countries and pursues a defensive policy," Defense Ministry spokesman Geng Yansheng said in a statement.

Geng said that China is modernizing its defense systems and armed forces only to safeguard national sovereignty, territorial integrity and to ensure smooth economic and social development.

The Japanese defense report contained "irresponsible comments", Foreign Ministry spokesman Ma Zhaoxu said late on Wednesday.

He asked Japan to focus on the economic opportunities brought by China's growth instead of Beijing's military modernization.

China has never, and will never, constitute a threat to any country, he said.

"We hope that the Japanese will use history as a guide and reflect on their defense policy earnestly and make more efforts to enhance mutual trust with their neighbors," Ma said.

The defense white paper is Japan's annual report evaluating its regional security environment but this year it paid special attention to China's maritime activity and for the first time mentioned the South China Sea, analysts said.

"Given the modernization of China's naval and air forces in recent years, its sphere of influence is likely to grow beyond its neighboring waters," the white paper said.

"It is expected that China will try to keep expanding its area of activity and to make naval activity routine practice in waters surrounding Japan, including the East China Sea and the Pacific Ocean, as well as in the South China Sea," it said.

Tokyo-based Kyodo News carried an article that said concerns over China's expanding military buildup can be seen everywhere in the white paper, The Defense of Japan 2011. It is obvious, the article said, that Japan intends to work with the Association of Southeast Asian Nations (ASEAN) countries to encircle China in a strategy based on the US-Japanese alliance.

An editorial published on Thursday's Nihon Keizai Shimbun (Nikkei) called for the strengthening of the US-Japanese alliance as well as cooperation with ASEAN countries, the Republic of Korea (ROK) and Australia. This strategy, the editorial said, is a "necessary step that Japan ought to take" to urge China to exercise "self-control".

Gao Hong, deputy director of the Institute of Japanese Studies with the Chinese Academy of Social Sciences, said that Japan has exaggerated "threats" from China for years in its annual defense white papers and that this year it even used the wording "high-pressure confrontation".

"Personally, I find the accusation does not have a leg to stand on. So-called high-pressure confrontation between states means a country uses its power to confine, force and even prosecute the other," Gao said.

He said that Japan, an island nation that has long pursued maritime interests due to limited resources, now feels more anxious and impatient following the earthquake and tsunami in March and the ensuing nuclear crisis.

The white paper was an attempt to shift attention from its domestic political problems and restore confidence following the events in March that caused a feeling of insecurity, even though the report will cause offense in neighboring countries, he said.

Wu Huaizhong, a researcher also with the Chinese Academy of Social Sciences, told People's Daily that Japan's efforts to play up the "China threat theory" is to boost its own defense spending.

"In order to get a bigger budget for its military buildup, it has to use neighboring countries, including China, as an excuse," he said.

Wu believed that the real "threat" to Japan is how to deal with the aftermath of the quake and tsunami.

Responding to Japan's mention about the South China Sea issue in its defense report, Li Jie, research fellow with the Naval Military Studies Research Institute, said it is a matter between China and the countries involved.

"China does not need a third country to add fuel to the fire," he said.

Japan's move has also angered other Asian countries, such as the ROK.

ROK officials on Tuesday slammed Japan's description of disputed islets in the Sea of Japan as its territory in the report. According to Yonhap News Agency, Japan has been using the same language since 2005 to refer to the disputed islets, known as Dokdo by the ROK and Takeshima by Japan.

The ROK foreign ministry said that Seoul would discuss countermeasures against Tokyo's latest claim. ROK President Lee Myung-bak is reportedly considering canceling a visit to Japan scheduled for later this year in protest.