"Ships of China’s maritime police acted within the law and took necessary measures, making a warning and driving [the ships] away," the coast guard agency said on social media.
China urged Japan to refrain from illegal action near the islands, which are claimed by both nations.
The contested islands are located east of Taiwan and are administered by Japan, which calls them the Senkaku Islands. China refers to them as the Diaoyu Islands.
Japan claims to have had sovereignty over the islands since 1895, while China argues that they were marked as Chinese territory on Japanese maps dated 1783 and 1785.
The United States took control over the islands during WWII and handed them over to Japan in 1972. China says that the islands were seized illegally by Japan, while Japan claims that China only became interested in them after shale oil was discovered under the seabed.