Taipei, Taiwan - Taiwan said Sunday it was on heightened alert after detecting "multiple waves" of missile firings in inland China, days after Beijing test-launched an intercontinental ballistic missile.

The defense ministry said it detected the firing by China's Rocket Force and army in the provinces and regions of Inner Mongolia, Gansu, Qinghai, and Xinjiang from 6:50 AM (6:50 PM ET on Saturday).

"The military has continuously monitored relevant developments, and the air defense forces maintain a high degree of vigilance and strengthen their alert," it said in a statement.

"The security and prosperity of the Indo-Pacific region are related to global development. Any threatening and provocative actions will seriously undermine regional stability," it added.

China China defends controversial ballistic missile launch as "legitimate and routine"

Beijing claims democratic Taiwan as part of its territory and has ramped up military and political pressure on the island in recent years.

Sunday's firings came after China said it test-launched an intercontinental ballistic missile on Wednesday, firing it into the Pacific Ocean in its first such exercise in decades.

The launch sparked protests from countries in the region, with Taiwan strongly condemning the action and urging Beijing to "exercise restraint and cease its reckless military drills which inflame regional tension".