China criticized new Defense Minister Gen Nakatani for the first time on Monday, saying it was "firmly opposed" to his comments that Beijing has repeatedly engaged in "dangerous actions" around the Senkaku Islands.
Although both countries reached an agreement late last year to reset ties, the comments by China's defense ministry underscore the fragile state of relations between Tokyo and Beijing.
Relations, which have long been poisoned by what China sees as Japan's failure to atone for its occupation of parts of China before and during World War II, have deteriorated sharply over the past 18 months because of the dispute over the Senkaku Islands in the East China Sea.
Gen Nakatani, a lawmaker who served in the Self-Defense Forces for several years, was appointed by Prime Minister Shinzo Abe in late December.
Nakatani has held the defense minister's post before and believes Japan should have the ability to hit enemy bases pre-emptively in the face of imminent attack.
Nakatani accused China last week of violating Japan's territorial waters with its vessels in the East China Sea, adding that China has locked fire-control radar on Japan's vessels and "flown its fighter jets abnormally close" to Japanese aircraft, in addition to setting up an air defense identification zone (ADIZ) in the East China Sea.
In a statement on its website, China's defense ministry hit back, saying its military activities in the sea and airspace were "completely legitimate."
"The leader of Japan's defense department ignores the facts and keeps on rehashing the same tune, playing up the 'China military threat,' " the ministry said. "China is firmly opposed to this."
The ministry reiterated its stance that China had a right to set up the ADIZ and that it has already clarified to Tokyo its use of radar.