"It is extremely disappointing and regrettable that the intrusions by Chinese official vessels have occurred frequently," Yoshihide Suga said Monday.
Kyodo News reported that four Chinese coast guard vessels sailed near the disputed Senkaku Islands Monday. The report said it was the 68th time such an incursion has occurred since the Japanese government staked its claim to part of the region last year.
China defends its policies in the area and officials said recent training missions for manned and unmanned aircraft were conducted according to international laws.
China's Xinhua News Agency quoted Defense Ministry spokesman Geng Yangsheng as saying Saturday, "Chinese aircraft have never infringed on other countries' airspace and China never allows other countries' aircraft to infringe on China's airspace."
Japan said recently it would shoot down any aircraft that strayed into its territorial airspace.
Geng said China reserved the right to retaliate if Japan shot at a plane.
China and Japan both claim jurisdiction over the East China Sea territories.
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