Taiwan's air force deployed missiles after as many as eight Chinese bomber planes and four fighter jets entered the southwestern part of its air defense identification zone on Saturday.
"Airborne alert sorties had been tasked, radio warnings issued and air defense missile systems deployed to monitor the activity," the island's defense ministry said, according to Reuters.
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China, which claims Taiwan as its own territory, has conducted almost daily flights over the waters between the southern part of Taiwan and the Taiwan-controlled Pratas Islands in the South China Sea in recent months.
However, they have generally consisted of just one or two reconnaissance aircraft.
The presence of so many Chinese combat aircraft on this mission - Taiwan said it was made up of eight nuclear-capable H-6K bombers and four J-16 fighter jets - was unusual.
A map provided by Taiwan's defense ministry showed that the Chinese aircraft, including a Y-8 anti-submarine aircraft, flew over the same waters where the most recent Chinese missions have been taking place near the Pratas Islands, though still well away from mainland Taiwan.
Taiwan's air force warned away the Chinese aircraft and deployed missiles to monitor them, the ministry said, using standard wording for how it responds to such activities.
The U.S. State Department urged China to stop pressuring Taiwan and reaffirmed its commitment to the island and desire to deepen ties.
"We urge Beijing to cease its military, diplomatic, and economic pressure against Taiwan and instead engage in meaningful dialogue with Taiwan's democratically elected representatives," State Department spokesman Ned Price said in a statement.
"We will continue to assist Taiwan in maintaining a sufficient self-defence capability."
There was no immediate comment from China. In the past, China has said it has been carrying out exercises to defend its sovereignty and security.
Taiwan's foreign ministry expressed its thanks for the show of U.S. support, adding they would work closely with the Biden administration to strengthen their close partnership.
Message to Biden Administration
Lo Chih-Cheng, a senior lawmaker for Taiwan's ruling Democratic Progressive Party who sits on parliament's foreign affairs and defense committee, told Reuters China was trying to deter the new U.S. government from backing the island.
"It's sending a message to the Biden administration," he said.
Beijing has watched with growing concern increasing U.S. support for democratic Taiwan, especially during Donald Trump's administration, which left office on Wednesday.
Last year, during visits by senior U.S. officials to Taipei, Chinese aircraft briefly crossed the median line of the Taiwan Strait, which normally serves as an unofficial buffer.
The flight by the Chinese bombers and fighters on Saturday came just days after Joe Biden assumed the U.S. presidency.
Emily Horne, spokeswoman for the White House National Security Council, said the U.S. commitment to Taiwan was "rock-solid" after the island's de facto ambassador in Washington, Hsiao Bi-khim, attended Biden's swearing-in on Wednesday.
