Taipei: China sent 27 aircraft to Taiwan's air defence identification zone (ADIZ), the island's Defence Ministry said on Wednesday hours after US House Speaker Nancy Pelosi left Taipei following a high-stakes visit that has spiked tensions in the Taiwan Strait.

As many as six J-11 fighter jets, five J-16 multirole fighters and 16 SU-30 multirole fighters entered the air defence zone today.

"27 PLA aircraft (J-11*6, J-16*5 and SU-30*16) entered the surrounding area of R.O.C. on August 3, 2022," Taiwan Defence Ministry tweeted.

This incursion after 21 Chinese military aircraft flew into the southwestern part of Taiwan's air defence zone on Monday night. In response to Chinese aggression, Taiwan sent an air patrol to monitor the situation, and also deployed anti-aircraft missile systems.

Pelosi's trip to Taiwan came to an end today as she departed from the self-ruled island after a short and gripping trip that upped the ante in the Taiwan Strait.

The US House Speaker, who is second in line to the Oval Office after the US vice-president, reaffirmed her country's unwavering commitment to supporting Taiwan's democracy and said this trip in no way contradicts longstanding United States policy on the self-governed island.

China, meanwhile, says Pelosi's Taiwan visit was a serious violation of the one-China principle and the provisions of the joint communique signed between the two countries.

On Tuesday, Chinese People's Liberation Army (PLA) announced missile tests and live firing as part of its military operations near Taiwan.

"The Chinese armed forces will begin military operations around Taiwan, long-range live firing will be held in the Taiwan Strait, and conventional missile tests will be organized in the sea area of the eastern part of the island," Sputnik news agency quoted Eastern Theatre Command spokesperson Shi Yi as saying.

"These actions are a fair deterrent to the recent major escalation of US negative actions on the Taiwan issue and a serious warning to the pro-Taiwan independence forces," Shi Yi said.

In the recent past, China has increased its use of grey zone tactics by routinely sending aircraft into Taiwan's ADIZ, with most occurrences taking place in the southwest corner.

In 2021, Chinese military planes entered Taiwan's ADIZ on 961 instances over 239 days.

Grey zone tactics are defined as "an effort or series of efforts beyond steady-state deterrence and assurance that attempts to achieve one's security objectives without resort to direct and sizable use of force."