US House Speaker Nancy Pelosi said Wednesday that her delegation had come to Taiwan in "peace for the region", after the visit enraged Beijing and set off a diplomatic firestorm.
She defied a string of increasingly stark warnings and threats from China, which views Taiwan as its territory and had warned it would consider her visit a major provocation.
Pelosi, second in line to the presidency, is the highest-profile elected US official to visit Taiwan in 25 years.
"We come in friendship to Taiwan, we come in peace to the region," she said during a meeting with Tsai Chi-chang, the deputy speaker of Taiwan's parliament.
As Pelosi -- who is on a tour of Asia -- touched down Tuesday night in a military aircraft after days of feverish speculation about her plans, the reaction from Beijing was swift.
US Ambassador Nicholas Burns was summoned by the Chinese foreign ministry and told that Washington "shall pay the price".
"The move is extremely egregious in nature and the consequences are extremely serious," China's Vice Foreign Minister Xie Feng was quoted as saying by state news agency Xinhua.
"China will not sit idly by."
The Chinese military said it was on "high alert" and would "launch a series of targeted military actions in response" to the visit.
It promptly announced plans for a series of military exercises this week in waters around the island, straddling vital shipping lanes.
The drills will include "long-range live ammunition shooting" in the Taiwan Strait, which separates the island from mainland China.
The zone of Chinese exercises will be within 20 kilometres (12 miles) of Taiwan's shoreline at some points, according to coordinates released by the Chinese military.
Taiwan's defence ministry said more than 21 Chinese military aircraft had flown on Tuesday into the island's air defence identification zone -- an area wider than its territorial airspace that overlaps with part of China's own air defence zone.
The ministry described the Chinese drills as "an attempt to threaten our important ports and urban areas, and unilaterally undermine regional peace and stability".
'We shouldn't be too worried'
Outside the Taiwanese parliament, 31-year-old computer programmer Frank Chen shrugged off the Chinese warnings against Pelosi's visit.
"I'm not too worried about China's intimidation," he told AFP.
"I think China will take more threatening actions and ban more Taiwanese products, but we shouldn't be too worried."
There was a small group of pro-China demonstrators outside parliament as well."The United States uses Taiwan as a pawn in its confrontation with China, to try to drag China down so (it) can dominate the world," Lee Kai-dee, a 71-year-old retired researcher, told AFP.
"If the United States continues to act this way, Taiwan will end up like Ukraine."
China has vowed to seize self-ruled, democratic Taiwan one day, by force if necessary.
Russia's invasion of Ukraine in February heightened fears in Taiwan that China may similarly follow through on its threats to annex the island.
Beijing tries to keep the island isolated on the world stage and opposes countries having official exchanges with Taipei.
In a call with US President Joe Biden last week, Chinese President Xi Jinping warned Washington against "playing with fire" on Taiwan.
While the Biden administration is understood to be opposed to Pelosi's Taiwan stop, White House National Security Council spokesman John Kirby said she was entitled to go where she pleased.
The United States has said, however, that its policy was unchanged towards Taiwan.
This means support for its government while diplomatically recognising Beijing over Taipei, and opposing a formal independence declaration by Taiwan or a forceful takeover by China.