The man was spotted shortly before 7:00 am (2300 GMT on Monday) off the main island of the Kinmen archipelago, the coast guard said in a statement.

The Kinmen islands are administered by Taipei but are located just a few kilometres from China's mainland.

"At 6:49 am today a Chinese male was found attempting to illegally enter Kinmen," the statement said.

The man was arrested by coast guard personnel and taken in for questioning. He would later be handed to Taiwanese prosecutors for investigation, it said.

A short time later, four China Coast Guard vessels were detected in waters around the Taiwan-controlled Matsu islands of Xiyin and Wuqiu.

"It can not be ruled out that this is related to the drills, or even part of the drills," the Taiwan coast guard said.

"It is very clear that China is adopting a hybrid approach of grey-zone harassment or military exercises."

Beijing insists democratic Taiwan is part of its territory and has threatened to use force to bring it under its control.

China's latest large-scale military drills around Taiwan come days after US Defense Secretary Pete Hegseth said the United States would ensure "credible deterrence" across the Taiwan Strait.

Beijing said Tuesday's exercises were aimed at practising for "precision strikes" and a blockade of the self-ruled island and to send a "stern warning" to alleged separatists in Taiwan.