"Sadly, Taiwan has been prevented from participating in global meetings, most recently the World Health Organisation, because of objections by the Chinese Communist Party," Pelosi said in statement.

"While they may prevent Taiwan from sending its leaders to global forums, they cannot prevent world leaders or anyone from travelling to Taiwan to pay respect to its flourishing democracy, to highlight its many successes and to reaffirm our commitment to continued collaboration."

China demonstrated its outrage over the highest-level US visit to the island in 25 years with a burst of military activity in surrounding waters, summoning the US ambassador in Beijing and halting several agricultural imports from Taiwan.

Some of China's planned military exercises were to take place within Taiwan's 12 nautical mile sea and air territory, according to Taiwan's defence ministry, an unprecedented move that a senior defence official described to reporters as "amounting to a sea and air blockade of Taiwan".

Taiwan scrambled jets on Wednesday to warn away 27 Chinese aircraft in its air defence zone, the island's defence ministry said, adding that 22 of them crossed the median line separating the island from China.

Pelosi arrived with a congressional delegation on her unannounced but closely watched visit late on Tuesday, defying China's repeated warnings, on a trip that she said demonstrated unwavering US commitment to Taiwan's democracy.

"Our delegation came to Taiwan to make unequivocally clear that we will not abandon Taiwan," Pelosi told Taiwan's President Tsai Ing-wen, who Beijing suspects of pushing for formal independence - a red line for China.

"Now, more than ever, America's solidarity with Taiwan is crucial, and that's the message we are bringing here today," Pelosi said during her roughly 19-hour visit.

She later arrived in South Korea, according to local media.

Australian Associated Press