The two Chinese vessels "openly intruded" into the waters around the Taiwan-controlled island, also known as Itu Aba, and stayed for 15 minutes before the Taiwanese coast guard expelled them, Taiwan's Coast Guard Administration said in a statement.

The coast guard expressed its "strongest condemnation of this incident", the statement said.

Taiping Island is the largest in the disputed Spratly archipelago, which is also claimed by China, the Philippines and Vietnam.

Its "prohibited" waters extend four kilometres (2.5 miles) from shore, the coast guard said.

The incident comes after China conducted a maritime operation in waters to the east of Taiwan, which the island democracy condemned.