Japan on Sunday joined the United States in criticizing China's new fishing restrictions in the South China Sea, saying the curbs, coupled with the launch last year of an air defense zone, has left the international community jittery.
Defence Minister Itsunori Onodera made the comment after observing the Japanese Self-Defence Forces' elite airborne brigade conducting airdrop drills designed to hone their skills to defend and retake remote islands.
Earlier on Sunday, Chinese government ships briefly entered what Japan considers its territorial waters near a group of disputed East China Sea islets, in the first such action this year.
"Setting something like this unilaterally as if you are treating your own territorial waters, and imposing certain restrictions on fishing boats is not something that is internationally tolerated," Onodera told reporters.
"I'm afraid not only Japan but the international society as a whole has a concern that China is unilaterally threatening the existing international order" with its new restrictions in the South China Sea and the creation of an air defense identification zone, he said.
(Read more: Ten trends that will shape Asia in 2014: Carnegie)
The fishing rules, approved by China's southern Hainan province, took effect on Jan. 1 and require foreign fishing vessels to obtain approval to enter disputed waters in the South China Sea, which the local government says are under its jurisdiction.
Washington called the fishing rules "provocative and potentially dangerous", prompting a rebuttal from China's foreign ministry on Friday.
Ties between China and Japan, the world's second- and third-largest economies, have been strained due to a long-running row over ownership of the group of tiny, uninhabited islands called the Senkaku in Japan and Diaoyu in China.
Tensions soared in recent months after Beijing announced the air defense identification zone covering a large swathe of the East China Sea, including the disputed isles, and Japanese Prime Minister Shinzo Abe visited a controversial Tokyo shrine seen by critics as a symbol of Japan's wartime aggression.
China and South Korea, where bitter memories of Japan's past militarism run deep, have repeatedly expressed anger in the past over Japanese politicians' visits to Yasukuni Shrine, where Japanese leaders convicted as war criminals by an Allied tribunal are honoured along with those who died in battle.
Stoking tensions further, three Chinese government ships on Sunday morning briefly entered what Japan sees as its territorial waters near the disputed islands, controlled by Japan but also claimed by China, the latest in such occasional entries by Chinese ships.
"We can never overlook such repeated entries. In addition to diplomatic efforts, we will cooperate with Coast Guard and securely defend our territory and territorial waters around the Senkaku," Onodera said.
Patrol ships from China and Japan have been shadowing each other near the islets on and off for months, raising fears that a confrontation could develop into a clash.