Meanwhile, hawkish Japanese Prime Minister Shinzo Abe and his key Cabinet members have made more tough remarks that may upset Japan's neighbors.

Despite Abe's claim on Sunday that he hopes to soon meet with the leaders of China and the Republic of Korea to improve relations strained by separate territorial disputes, his ruling Liberal Democratic Party also pledged on the same day to push for changes to Japan's pacifist Constitution.

The Constitution's revision has long been viewed as a move "likely to stir unease" in Japan's Asian neighbors, including China and the ROK, which were among the victims of Tokyo's 20th-century militarism, Reuters commented.

Japanese Chief Cabinet Secretary Yoshihide Suga said on Monday that Tokyo stressed the importance of the "strategic and mutually beneficial relationship", but Tokyo hasn't changed its persistent stance of denying the existence of the Diaoyu Islands row.

Yang Bojiang, an expert on Japanese studies at the Chinese Academy of Social Sciences, warned about Japan's dubious vow of enhancing the "strategic and mutually beneficial relationship" between Japan and China.

"Given Abe's series of attempts to whitewash Japan's militarist past, including denying the country's wartime deeds of forcing Asian women into sexual slavery, we should have a closer look and doubt Tokyo's sincerity" about improving ties, Yang said.

Japan is "vulgarizing" the concept of the "strategic and mutually beneficial relationship", Yang warned.

Abe also warned against ongoing "provocations" against Japanese territory and said the Japanese Self-Defense Forces are facing "a crisis of the here and now," when addressing a Sunday graduation ceremony at the National Defense Academy, Japan's NHK Television reported.

Japanese Defense Minister Itsunori Onodera referred on Saturday to China's maritime presence when he underlined the necessity of enhancing the armed forces.