Taiwan's defence ministry said it also spotted Chinese coast guard vessels in its waters.
Taiwan's military is on high alert after detecting Chinese warships near the island.
Beijing has vowed to "firmly defend" its sovereignty in response to the drills.
Taiwan's defence ministry said it also spotted Chinese coast guard vessels and that Beijing's People's Liberation Army had restricted the airspace off the Chinese coast.
There has been intense speculation about the possibility of China launching military drills in response to Taiwanese President Lai Ching-te's trip to the Pacific which included stopovers in Hawaii and Guam.
There was no immediate public announcement by the PLA or Chinese state media about increased military activity around Taiwan.
Taiwan regards itself as a sovereign nation with its own government, military, and currency.
But Beijing insists the island is part of its territory and has not ruled out using force to bring it under its control.
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