China has deployed fighter jets, warships and coast guard vessels around Taiwan, which Beijing claims as part of its territory, in its latest large-scale drills.

The man was detected Monday morning in a rubber boat making the "illegal crossing" to the tiny island of Menghu, the coast guard said in a statement.

"It is not ruled out that the small boat stowaway attempt could be a grey zone intrusion linked to the military exercise," the coast guard said in a statement, referring to tactics which fall short of a direct act of war.

Menghu, which is part of the Taipei-administered Kinmen islands, is about six kilometres (four miles) from mainland China's port city of Xiamen in Fujian province.

Video released by Taiwan's coast guard showed its personnel tying the man's wrists with plastic zip ties and escorting him onto a vessel.

The man and his boat were taken to Kinmen for investigation.

The man said he was in his 40s and from China's southern province of Guangdong, and was "seeking freedom due to political persecution", a coast guard officer told AFP on the condition of anonymity.

The coast guard said it had "heightened its vigilance" and was constantly monitoring "security hotspots" and carrying out "real-time tracking of maritime targets".