The defense ministry said in a statement that 32 aircraft from the People’s Liberation Army and nine vessels from the navy were detected in the 24 hours between 6 a.m. Friday and 6 a.m. Saturday.

Of these, 20 aircraft either crossed the median line of the Taiwan Strait or breached Taiwan’s air defense identification zone. In response, Taiwan tasked its own aircraft, vessels and missile systems to respond to the activities, the defense military said.

In the past year, Beijing has stepped up military drills around the island in reaction to Taiwan’s political activities. The Chinese military launched drills around Taiwan last week as a “stern warning” after Taiwan’s vice president stopped over in the U.S. while on an official trip to Paraguay.

The State Department said Wednesday it had signed off on the sale of infrared search and track systems for F-16 fighter jets and other related equipment to Taiwan worth half a billion dollars.

Chinese Defense Ministry spokesperson Zhang Xiaogang said Friday that China opposed the arms sale, calling it a “gross interference” in China’s internal affairs and describing it as a “heinous act” that violates its “One China” principle, as well as three Sino-U.S. joint communiques. Zhang also said that China urged the U.S. to fulfill its commitment of not supporting the independence of Taiwan.