Taiwan lives under constant threat of invasion by China, which views the self-ruled island as part of its territory to be seized one day.

On Saturday, Taiwan's defence ministry said 19 Chinese warplanes including J-10 and J-16 fighters were detected around the island.

Eight of them crossed the median line of the Taiwan Strait and approached the island's contiguous zone, or the band of sea within 24 nautical miles (44 kilometres) of its coast, the ministry said in a statement.

"Additionally, five PLAN (Chinese navy) vessels conducted joint combat patrol," it continued, adding that it was closely monitoring the situation and had deployed its patrol aircraft and vessels in response.

Beijing has ramped up incursions into Taiwan's air defence identification zone (ADIZ) in recent years as relations between the two sides have plunged.

Taiwanese Defence Minister Chiu Kuo-cheng warned in March that Beijing could use a potential visit by US House Speaker Kevin McCarthy as an excuse to cross into Taiwan's contiguous zone and approach its territorial space, defined as being within 12 nautical miles of the coast.

McCarthy instead met Taiwanese President Tsai Ing-wen in California in April, prompting China to launch three days of military exercises around the island that included simulating targeted strikes and practising a blockade.

On the final day of the drills, Taiwan detected 12 Chinese warships and 91 aircraft around the island, with 54 planes entering its southwestern and southeastern ADIZ.

The ADIZ is not the same as Taiwan's territorial airspace, and includes a far greater area that overlaps with part of China's own ADIZ and even some of the mainland itself.