China flew 28 warplanes around Taiwan on Sunday, with most crossing the median line of the Taiwan Strait for unspecified "long-range" missions, Taipei authorities said.

Taiwan's defense ministry said 20 of the aircraft detected since Sunday morning crossed the median line of the waterway separating Taiwan and mainland China, and entered the self-ruled island's southeast and southwest air defense identification zone.

China was conducting "missions such as long-range exercises and training", the defense ministry said in a statement, adding that it was monitoring the situation with patrol aircraft and ships.

Beijing claims democratic Taiwan as its own territory to be seized one day, by force if necessary. It has stepped up military and diplomatic pressure on the island in recent years as relations have soured.

Last week, Taipei reported an increased number of incursions by Chinese warplanes and ships, after Beijing said its troops were on "high alert" following two ships belonging to the United States and Canada transiting through the Taiwan Strait this month.

Taiwan's defense ministry said 68 Chinese aircraft and 10 naval vessels were detected around the island between Wednesday morning and Thursday morning.

Some of those planes and warships were heading to an unspecified area of the Western Pacific to "conduct joint sea and air training" with China's Shandong aircraft carrier, the ministry said.

The Shandong, one of two operational aircraft carriers in the Chinese fleet, was detected Monday around 60 nautical miles (110 kilometers) southeast of Taiwan heading into the Western Pacific, Taipei authorities said.

China has not commented officially on any drills being conducted in the Western Pacific.

In April, Beijing conducted military exercises to simulate the encirclement of the island, after Taiwan's President Tsai Ing-wen met US House Speaker Kevin McCarthy in California.

At the time, Taiwan detected 71 Chinese warplanes in a 24-hour period, matching the record daily high set in December 2022.