China has moved its army, naval, air force and rocket force units to surround Taiwan for military drills, warning outside forces against supporting Taiwanese independence.
The operation, dubbed "Justice Mission 2025", aims to test Beijing's combat readiness, and will involve live-fire exercises on Tuesday.
China's Eastern Theatre Command said five zones surrounding Taiwan would be under sea and air space restrictions for 10 hours from 8.30am local time (11.30am AEDT).
The statement included a graphic detailing the five zones surrounding the island.
"This serves as a serious warning to 'Taiwan Independence' separatist forces and external interference forces," Shi Yi, a spokesperson for the Eastern Theatre Command said.
"The exercise focuses on training for maritime and aerial combat readiness patrols, gaining integrated control, sealing off key ports and areas and conducting multi-dimensional deterrence."
Taiwan's government condemned the drills with a presidential office spokesperson urging China to not undermine regional peace, and called on Beijing to immediately stop what they described as irresponsible provocations.
The island's defence ministry said two Chinese military aircraft and 11 ships had been operating around the island over the last 24 hours, and that Taiwan's military was on high alert and poised to carry out "rapid response exercises".
That particular drill is designed to move troops swiftly in case China suddenly turns one of its frequent drills around the island into an attack.
"All members of our armed forces will remain highly vigilant and fully on guard, taking concrete action to defend the values of democracy and freedom," it said in a statement.
A senior Taiwan security official told Reuters dozens of Chinese military boats and planes were operating near Taiwan on Monday, and some of them were "deliberately closing in" to Taiwan's contiguous zone.
Beijing views Taiwan as a part of China and, according to a US Pentagon report, wants to be in a position where it could take the territory by 2027.
However Taiwan, a self-governed island, rejects China's claimed sovereignty, maintaining that only its people can decide the island's future.
Taiwan's Civil Aviation Administration said more than 100,000 air passengers will be affected by the live-fire drills.
"Tomorrow (Tuesday) … scheduled flights, including about 296 international departures, around 265 international arrivals and roughly 296 transit flights," will be affected, the administration said.
Military actions days after US arms deal with Taiwan
The drills represent the sixth major round of war games since 2022 after then-US House speaker Nancy Pelosi visited Taiwan.
Last year, the Chinese People's Liberation Army practised port blockades around Taiwan during its war games.
But this marked the first time it has publicly stated that drills around the island are aimed at "deterrence" of outside military intervention.
It comes just 11 days after the United States approved $US11.1 billion ($16.68 billion) in arms sales to Taiwan.
It was the largest ever US weapons package for the island, and the second arms sale announcement of the current Trump administration.
It also follows growing hostilities in the region over Beijing's territorial claims as Japan's Prime Minister Sanae Takaichi suggested a hypothetical Chinese attack on Taiwan could trigger a military response from Tokyo.
China wants to 'keep the island, not the people'
Following the announcement of the drills, the Chinese military released two posters titled "Shields of Justice: Smashing Illusions," and "Arrows of Justice: Control and Denial".
"Any foreign interference that touches the shield (of justice) shall perish!" the poster read.
"Any separatist scoundrels who encounter the shield shall be destroyed!"
The increasing tensions worried 56-year-old Taiwanese interior designer Stephanie Huang who said Bejing's goal was to "keep the island, not the people."
"They just want to save face by claiming Taiwan as part of their own country, but Taiwanese people don't see it that way," she said.
"We are who we are, they are who they are. The two sides of the strait are completely not subordinate to each other.
"We are our own country. We have a president, we have our own constitution and we have our own legislature. I believe we are a completely independent nation."
ABC/Wires
