Taiwan scrambled its jets on Saturday after Chinese ships and planes practiced an attack on the island.
There were 20 Chinese aircraft and 14 warships in the Taiwan Strait on Saturday.
Fourteen of the 20 Chinese aircraft crossed the median line, which is an unofficial buffer between China and Taiwan.
The army broadcast a warning and put shore-based missiles on stand-by, according to the ministry.
According to a source familiar with security planning, off Taiwan's east coast, Chinese warships and drones practiced attacking US and Japanese warships.
China's Eastern Theater Command has been conducting sea and air exercises near Taiwan to test their land strike and sea assault capabilities.
The Chinese exercises, which include live-fire drills, are scheduled to continue into Sunday. Nancy Pelosi visited Taiwan, which China claims as its own territory.
Insider previously reported that Beijing had warned of a possible military reaction to Pelosi's visit.
Missiles have been fired over and around Taiwan.
Taiwan's defense ministry said that China deployed aircraft and vessels in the Taiwan Strait. This is indicative of the recent increase in tensions in the region.