ANKARA (AA) – The Chinese army encircled Taiwan from four directions on Saturday morning during the first day of a three-day military exercise, in apparent response to Taiwanese President Tsai Ing-wen's visit to the US.

According to the Chinese People's Liberation Army (PLA) Eastern Theater Command, they began the exercises by encircling Taiwan from four directions with combat alert patrols and joint exercises, which are scheduled to last until Saturday, the state-run Global Times reported.

"This is a stern warning to ‘Taiwan independence’ secessionist forces and their collusion with external forces, and a necessary move to safeguard national sovereignty and territorial integrity," the daily said, citing a statement from PLA Eastern Theater Command spokesman Senior Colonel Shi Yi.

The latest development came after Tsai Ing-wen returned home on Friday from a 10-day trip to Central America and the US, where she met with US House Speaker Kevin McCarthy in California and received a global leadership award from a think tank in New York.

Earlier on Friday, China sanctioned two US institutions, including the Hudson Institute, which presented the Taiwanese leader with the award, and the Ronald Reagan Presidential Foundation and Institute, where she met with the US House speaker.

Beijing said the two American institutions were “banned from having any exchanges, cooperation, and other activities with any individuals, universities or institutions in Beijing’s territory, including Hong Kong and Macau.”

“In disregard of China’s repeated representations and firm opposition, the United States insisted on allowing Taiwan leader Tsai Ing-wen to ‘transit’ to the United States to engage in political activities from March 29 to 31 and April 4 to 6, 2023,” said the Chinese Foreign Ministry.

Meanwhile, Taiwan’s Defense Ministry said in a statement that they have detected Chinese vessels entering the region designated as an air defense identification area (ADIZ).

"42 PLA aircraft and 8 vessels were detected by 11:00 a.m. (UTC+8) April 8th. 29 of the detected aircraft had crossed northern, central, and southern median line of the #TaiwanStrait and entered our southwest #ADIZ, attempting coercion on us," the ministry stated on Twitter.

Beijing considers Taiwan as its “breakaway province” and has strongly urged other nations to avoid direct relations with Taipei -- which enjoys independent diplomatic relations with 13 countries.

The US does not recognize Taiwan as a separate nation but maintains economic and defense ties with the island.

In response to US House Speaker Nancy Pelosi's visit to Taiwan last year, China conducted massive military drills and live firing in the waters and airspace surrounding Taiwan.

Republican Newt Gingrich was the last US House Speaker to travel to Taiwan, in 1997.