Taiwan's defence ministry reported a spike in Chinese military activity around the island on Wednesday, including 53 military aircraft, with Taiwan on high alert over Beijing's latest pressure campaign.
China's military has yet to comment and has not confirmed it is carrying out any military exercises.
China, which views democratically governed Taiwan as its own territory, had been expected to launch drills to express its anger at President Lai Ching-te's tour of the Pacific that ended on Friday, which included stopovers in Hawaii and the US territory of Guam.
On Tuesday, Taiwan's defence ministry said China was deploying its largest navy fleet in regional waters in nearly three decades, posing a threat to Taiwan that is more pronounced than previous Chinese war games.
A US military official said China's naval deployments in the East China Sea and South China Sea are elevated but consistent with other large exercises in the past.
On Wednesday, Taiwan's defence ministry said it detected 53 military aircraft operating around the island over the past 24 hours, as well as 11 navy vessels and eight "official" ships, which refers to vessels from ostensibly civilian agencies such as the coast guard.
Taiwan's military had gone on alert on Monday after saying China had reserved airspace and deployed naval and coast guard vessels.
Lai and his government reject Beijing's sovereignty claims, saying only Taiwan's people can decide their future.
China says the Taiwan issue is the "core of its core interests" and a red line the United States should not cross.
China has held two rounds of major war games around Taiwan so far this year.
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