The Chinese coast guard said its vessels sailed through waters near the Diaoyu Islands (called Senkaku by Japan) on Tuesday and that the formation was a "rights patrol", Reuters reported.
The Chinese coast guard said in a statement that its actions were in accordance with international law.
China and Japan have been locked in a dispute over the Japanese-controlled islands for years.
Tensions between the two countries have escalated since Japanese Prime Minister Sanae Takaichi said on November 7 that if Taiwan were attacked, it could justify sending Japanese troops to defend the island.
The Chinese military has threatened Tokyo with retaliation "crushing defeat" if it tries to intervene in Taiwan, and yesterday China advised its citizens to avoid travel to Japan.