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 position Beijing considers unacceptable.

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.

Taiwan was among the issues discussed by US President Joe Biden and Chinese leader Xi Jinping in a call on Tuesday.

The White House said Biden pressed Xi to ensure "peace and stability" across the Taiwan Strait ahead of the Lai inauguration.

Xi told Biden that Taiwan remains "an uncrossable red line" for Beijing, according to Chinese state media.

The United States switched recognition in 1979 from Taipei to Beijing, but remains a key partner of the island.

The US Congress in 1979 passed a law that requires the United States to provide weapons to Taiwan to defend itself and ensures that the island's representatives in the United States are treated as foreign diplomats in all but name.

China does not maintain relations with countries that recognise Taiwan and has stepped up efforts to diplomatically isolate Taipei in recent years.

In January, the tiny South Pacific nation of Nauru switched recognition from Taipei to Beijing.

That left only 12 states, including the Vatican, that fully recognise Taiwan.