Chinese air force planes including 12 fighter jets enter Taiwan's air defence identification zone for a second day, Taiwan says, just days into US President Joe Biden's new administration.
The United States' commitment to Taiwan is "rock-solid", the State Department has said, as Taiwan reported another day of "incursions" by more than a dozen Chinese aircraft.
A total of 15 Chinese aircraft including 12 fighter jets entered the southwestern corner of Taiwan's air defence identification zone on Sunday, the island's Defence Ministry said.
A map provided by the ministry showed the Chinese aircraft again flew in between the southern part of Taiwan and the Taiwan-controlled Pratas Islands in the South China Sea.
On Saturday, Taipei reported "incursion" of eight nuclear-capable H-6K bombers, four J-16 fighter jets, and Y-8 anti-submarine aircraft in its airspace.
Beijing hasn't commented yet.
READ MORE: The South China Sea dispute explained
Biden administration vows support to Taipei
US State Department spokesperson Ned Price said it "notes with concern the pattern of ongoing PRC [People's Republic of China] attempts to intimidate its neighbours, including Taiwan" and "urges Beijing to cease its military, diplomatic, and economic pressure against Taiwan".
The statement added Washington would continue to work on "deepening" ties with democratic Taiwan.
Taiwan split from China at the end of a civil war in 1949. Its 23 million people live under the constant threat of invasion by the mainland, whose leaders view the island as their territory and have vowed to one day take it.
Washington diplomatically recognises Beijing over Taipei, but remains the latter's most important unofficial ally and military backer.
Beijing baulks at any official contacts with Taiwan and tries to keep the island diplomatically isolated.
President Donald Trump embraced warmer ties with the island as he feuded with China on issues like trade and national security.
Beijing's warning to Biden administration
Beijing has called for a reset in US-China ties under Biden and on Thursday warned the US to "cautiously and appropriately handle Taiwan issues to prevent harm to US-China relations".
But the new US president is expected to remain tough on the superpower rival despite a softening of diplomatic tone.
Protecting Taiwan has become a rare bipartisan issue, especially as Chinese President Xi Jinping has ramped up threats towards the island.
Last year, Chinese airplanes made a record 380 incursions into Taiwan's air defence identification zone and there is little sign of a shift since Biden came to power.
In a tweet on Sunday, Taipei's Ministry of Foreign Affairs thanked the US for its statement of support "in the face of Beijing's ongoing coercion."
In a subtle but symbolic gesture, Taiwan's de facto ambassador to the US was formally invited to Biden's inauguration in what Taipei said was a precedent-setting first since Washington switched recognition to Beijing in 1979.