Taiwan’s Defense Ministry said Saturday that it detected three Chinese warships, including the Shandong aircraft carrier, passing through the Taiwan Strait, as Beijing keeps up pressure on the self-ruled island it claims as its own.

The ministry said it was monitoring the movements of the ships and will respond accordingly. In a tweet, the ministry said that the three vessels were headed north along the Taiwan Strait at noon and were steering along the west of the median line — an unofficial boundary once tacitly accepted by both sides.

China has stepped up its military activities around Taiwan in recent months amid deteriorating U.S.-China ties.

China claims Taiwan as its own territory to be brought under its control by force if necessary and regularly sends ships and warplanes into airspace and waters near the island.

The ministry also said that in the 24 hours from 6 a.m. Friday to Saturday, it detected 33 of China’s People’s Liberation Army aircraft and 10 navy vessels around Taiwan. Twelve of the aircraft had crossed the median line of the Taiwan Strait or entered the island’s air defense identification zone.

In response, Taiwan’s armed forces deployed aircraft, navy vessels and land-based missile systems.

In April, the Chinese military said it was “ready to fight” after completing three days of large-scale combat exercises around Taiwan that simulated sealing off the island in response to Taiwanese President Tsai Ing-wen’s trip to the U.S.

Last August, China intensified war games around Taiwan, with missile firings and incursions into Taiwanese waters and airspace following then-House Speaker Nancy Pelosi’s visit to Taipei.

(AP)