Sirens blare across Taiwan, streets are cleared and people moved into shelters as the island carries out military drills amid growing concerns over China's warning over US Speaker's likely visit to the region, which it claims as its own.
The Russia's February invasion of Ukraine has sharpened those concerns.
China has reacted strongly to reports that US House Speaker Nancy Pelosi may visit Taiwan on Tuesday, warning that its military would never "sit idly by" if she were to visit the island.
Ms Pelosi's office said on Sunday that she was leading a congressional delegation to the region that would include visits to Singapore, Malaysia, South Korea and Japan. It did not mention Taiwan.
Chinese foreign ministry spokesman Zhao Lijian said earlier on Monday that it would be "a gross interference in China's internal affairs" if Pelosi visits Taiwan, and warned that it would lead to "very serious developments and consequences."
China views visits by US officials to Taiwan as sending an encouraging signal to the pro-independence camp in the island.
A visit by Ms Pelosi would come amid worsening ties between Washington and Beijing. Republican Newt Gingrich was the last House speaker to visit Taiwan, in 1997.
In a call with US President Joe Biden last Thursday, Chinese President warned him that Washington should abide by the one-China principle and "those who play with fire will perish by it".
Biden told Xi that US policy on Taiwan had not changed and that Washington strongly opposes unilateral efforts to change the status quo or undermine peace and stability across the Taiwan Strait.
Beijing considers Taiwan to be part of its territory and has never renounced using force to bring the island under its control. Taiwan rejects China's sovereignty claims and says only its people can decide the island's future.