China had warned against the visit by Pelosi, who is second in the line of succession to the U.S. presidency and a long-time critic of Beijing.
In the latest warning from Beijing, Chinese Foreign Minister Wang Yi said on Tuesday that U.S. politicians who "play with fire" on the Taiwan issue will "come to no good end".
Meanwhile, China's Defence Ministry said on Tuesday night that Chinese military has been put on high alert and will launch "targeted military operations" in response to the visit.
Separately, the People's Liberation Army's Eastern Theatre Command said it will conduct joint military operations near Taiwan, and will test-launch conventional missiles in the sea east of Taiwan.
Pelosi and her delegation disembarked from a U.S. Air Force transport plane at Songshan Airport in downtown Taipei and were greeted by Taiwan's Foreign Minister Joseph Wu and Sandra Oudkirk, the top U.S. representative in Taiwan, according to Reuters.
"Our congressional delegation's visit to Taiwan honors America's unwavering commitment to supporting Taiwan's vibrant democracy," Pelosi said in a statement shortly after landing. "America's solidarity with the 23 million people of Taiwan is more important today than ever, as the world faces a choice between autocracy and democracy."
Pelosi was on a tour of Asia that includes announced visits to Singapore, Malaysia, South Korea and Japan. Her stop in Taiwan had not been announced but had been widely anticipated.
China considers Taiwan as part of its territory and views visits by foreign government officials as recognition of the island’s sovereignty. The United States has no official diplomatic relations with Taiwan but is bound by American law to provide the island with the means to defend itself.
Reacting to the trip, Iran’s Foreign Ministry spokesman Nasser Kanaani condemned the move. He said the U.S. “provocative” move in interfering China’s internal affairs and violating the country’s territorial integrity is an example of Washington’s interferences in countries’ internal affairs. Kanaani stressed that such moves have no result but increasing instability.
Russia also censured Pelosi's visit. Maria Zakharova, Russia's Foreign Ministry spokeswoman, said the visit was a provocative U.S. attempt to pile pressure on China.
"The USA is a state provocateur," Zakharova said. "Russia confirms the principle of 'one China' and opposes the independence of the island in any form."