Taiwan on Sunday condemned what it called a “provocative” move by China after two Chinese fighter jets crossed a maritime border separating the two sides amid growing friction between them.

Earlier on Sunday Taiwan scrambled aircraft to drive away the two Chinese planes, the self-ruled island’s defense ministry said.

China’s move “seriously impacted regional safety and stability,” the ministry said in a statement.

There was no immediate reaction from Beijing, which views Taiwan as part of its territory.

Huang Chung-yen, a spokesman for Taiwan’s Presidential Office, said China “should stop behavior of this sort, which endangers regional peace, and not be an international troublemaker.”

China has repeatedly sent military aircraft and ships to circle Taiwan during drills in recent years and worked to isolate the island internationally, whittling down its few remaining diplomatic allies.

Last week the United States sent Navy and Coast Guard ships through the Taiwan Strait, a strategic waterway, as part of an increase in the frequency of movement there despite opposition from China.

Taiwan is one of a growing number of divides in China’s relationship with the United States, which also include a trade war and China’s increasingly muscular military posture in the South China Sea.

China has never renounced the possibility of using force to bring Taiwan under its control.