China claims self-ruled Taiwan as its territory and has maintained it will seize it one day -- by force, if necessary.

Beijing performs near-daily aerial incursions around the island, and on Monday Taiwan's defence ministry reported a "recent high" of 103 warplanes within a 24-hour window.

"Our enemy's recent movements are really quite abnormal," Taiwan's defence minister Chiu Kuo-cheng told reporters outside parliament in Taipei on Friday.

"Our initial analysis is that up to September, they have been doing joint exercises, including land, sea, air and amphibious," he said.

His comments came a day after the ministry flagged that it was "monitoring (China's) long-range artillery, rocket forces and ground troops around Fujian province's Dacheng Bay" -- an area facing the island across the Taiwan Strait.

"The threat posed by PLA's (People's Liberation Army) activities have led to an escalation of tension and damaged the regional security," said ministry spokesman Sun Li-fang on Thursday, referring to the Chinese military.

"The closer the PLA's aircraft are to Taiwan, the stronger our countermeasures will be."

China has made no official comment on Monday's massive show of force, although its state tabloid Global Times said the "relevant combat training activities are necessary actions to safeguard national sovereignty".

Since Monday, dozens more planes have been detected around Taiwan, with many briefly crossing a so-called median line bisecting the Taiwan Strait -- a 180-kilometre (110-mile) waterway separating the island from China.

On Friday morning, the defence ministry said 32 Chinese aircraft were detected within the previous 24 hours, publishing a map that illustrated the flight path of 17 planes crossing the median line.

Two of them ventured around Taiwan's southern tip, according to the map.

Earlier this week, US officials from the Pentagon said a direct invasion by China would not be easy due to Taiwan's mountainous terrain and lack of landing beaches.

They also said combining amphibious and airborne assault operations would be "extremely complicated".