Japan expressed concern on Tuesday over the Chinese military's recent maritime activities in its annual defense report, a week after Beijing officially announced its aircraft carrier program.

"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 annual white paper said.

"It is expected that China will try to keep expanding the area of activities, and to make its naval activities a 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.

The report, approved by Japanese Prime Minister Naoto Kan's cabinet, described China's stance in its maritime territorial disputes with its neighbors as "assertive".

"This is one way of expressing our hope that China will address these issues through friendly relations," Japanese Defense Minister Toshimi Kitazawa told reporters.

Liu Jiangyong, a professor of East Asia studies at Beijing-based Tsinghua University, said that the defense white paper is Japan's annual report evaluating the security environment surrounding the country, adding that this year it paid more attention to China's maritime activities.

"Japan expresses further concerns about the South China Sea," Liu said after analyzing some of changes in the newly released white paper, adding that, along with Washington, it was talking up the so-called freedom of navigation issue.

"But China has never broken international laws when protecting its territory and sovereignty."

Liu told China Daily the passing of Chinese vessels near Japan's Miyako Islands did not do any harm to Tokyo and such activities within a country's economic zone are legally allowed.

"Actually, it is Japan and the US that are sparing no efforts to limit China in the East China Sea and restrict its navigational freedom," Liu stressed.