China considers self-ruling Taiwan its territory, and has never renounced the use of force to bring the island under its control.

Taiwan's defence ministry said 20 of the aircraft crossed into the island's so-called Air Defence Identification Zone (ADIZ).

Taiwan's armed forces "monitored the situation and employed (patrol) aircraft, Navy vessels, and coastal missile systems in response to the detected activities", it said in a statement.

Last month, Taiwan detected 36 Chinese warplanes around the island over a 24-hour period, the highest daily count this year.

The uptick in incursions follows a pattern of what experts dub "grey zone" actions -- moves that fall short of outright acts of war.

These have ramped up since the 2016 election of President Tsai Ing-wen, who considers Taiwan "already independent" -- a red line for Beijing.

China deploys warplanes and naval vessels around Taiwan on a near-daily basis, and balloon flights over the island have also increased.

Taiwan's current Vice President Lai Ching-te -- who is disliked by Beijing -- won the January 13 presidential election.

Lai and Vice President-elect Hsiao Bi-khim of the ruling Democratic Progressive Party (DPP) will take office on May 20.