A Chinese military statement said the People’s Liberation Army will conduct combat exercises in the north, east, south and west of Taiwan Island and its airspace in the Taiwan Strait from April 8 to 10.

Taiwan’s Ministry of Defense later announced that it had observed three warships and 13 Chinese aircraft around the island. “Four of the 13 aircraft were found to have violated Taiwan’s air defense zone in the southeast,” the ministry said in its daily update.

China had already imposed sanctions on Friday against two US organizations that hosted Taiwanese President Tsai Ing-wen during her visit to the US. During that trip, Tsai also met Republican House Speaker Kevin McCarthy.

Self-governing democratic Taiwan, which is not part of the People’s Republic of China, has had an independent government since 1949. However, China considers the island, which has a population of about 23 million, as part of its territory. China reiterated on Friday that Taiwan is an “inalienable part of China”. Beijing had already indicated it would respond “firmly” ahead of the meeting with McCarthy. When McCarthy’s predecessor, Nancy Pelosi, visited Taiwan last summer, massive Chinese military exercises around the island also continued.

There have been various tensions between the two countries for the past few months. After the Russian invasion of Ukraine, there is great concern in the West that China may also use military force in its territorial claims on Taiwan.