Beijing claims democratic Taiwan as its own territory and has never renounced the use of force to bring the self-ruled island under its control.

Since the 2016 election of Taiwanese President Tsai Ing-wen, Beijing has ramped up military pressure, sending in warplanes and vessels around the island in what experts call "grey zone" actions -- tactics that fall short of an outright act of war.

In recent months, the defence ministry began reporting sightings of Chinese balloons around Taiwan, with some moving directly above the island, and last week, Taiwan detected 11 naval vessels around it -- the highest number so far this year.

Taipei's defence ministry said in a report to parliament Thursday that Beijing had "intensified its military intimidation", saying the drones and ballons sent around Taiwan and its outlying islands were a way to "collect intelligence".

China's "frequent intrusions into our territorial waters and airspace with balloons, drones, and civilian ships (aim) to carry out diversified saturated grey zone harassment against us," it said.

It also said Beijing was using maritime survey ships as a "civilian" method of disguising "military activities", while sending in coast guard forces and naval vessels was aimed at exhausting Taiwan's sea and air forces.

The incursions were an attempt to "obscure the existence of the median line of the Taiwan Strait", the report said, referring to a tacit boundary in the middle of the 180-kilometre (110-mile) waterway separating China from Taiwan's main island.

China does not recognise the median line.

Relations between the two sides have plummeted since Tsai's election, as she and her Democratic Progressive Party do not recognise Beijing's claim on Taiwan.

Her deputy Lai Ching-te -- who Beijing has called a "dangerous separatist" -- won the island's January presidential election and will be inaugurated in May.

Adding to tensions was a fatal incident near Taiwan's Kinmen island last month -- which is geographically closer to mainland China -- in which a fishing boat carrying four Chinese crew members capsized when being pursued by Taipei's coast guard. Two members died.

Taiwan had defended the coast guard actions as following procedures after the Chinese boat entered "prohibited waters", but Beijing accused them of "seeking to evade their responsibilities and hide the truth".

Taiwan's coast guard chief said Monday that an average of six to seven Chinese vessels have been in waters around Kinmen daily since the boat incident.