China's Ministry of National Defense on Tuesday urged the U.S. to stop provocative acts against its Taiwan region, after some members of the U.S. Congress visited the island via military aircraft earlier in the day.

"We are hereby expressing our firm opposition and strong condemnation," Defense Ministry spokesperson Tan Kefei said in a statement.

The acts of the U.S. side have wantonly interfered in China's internal affairs while damaging China's sovereign rights, he said, calling for an "immediate stop" to all "destructive activities" that may heighten the situation across the Taiwan Straits.

Tan warned that the country's armed forces, the People's Liberation Army (PLA), will stay on high alert and adopt "any necessary measures" needed to counter external interference from foreign parties and the "Taiwan independence" forces.

Later, China's PLA Eastern Theater Command announced that they had conducted patrol near the Taiwan Straits, in a move to "further examine the enhancement of cooperative abilities of multi-type forces."

The military operation this time was a "necessary move" to safeguard the country's sovereignty, said Shi Yi, spokesperson for the Eastern Theater Command, in a statement.

The Eastern Theater Command will resolutely attack any provocative acts that endanger China's core interests and damage the peace and stability of the Taiwan Straits, he added.