The sorties come weeks before the May 20 inauguration of new Taiwan president Lai Ching-te, who China regards as a dangerous separatist.

A statement from the defence ministry said 17 of the aircraft "crossed the median line and entered Taiwan's northern and central ADIZ (air defence identification zone).

The line bisects the Taiwan Strait, a narrow 180-kilometre (110-mile) waterway separating the island from mainland China.

Beijing, which does not recognise the line, claims democratic Taiwan as part of its territory and has never renounced the use of force to bring the island under its control.

Under the administration of Taiwanese President Tsai Ing-wen, tensions between Beijing and Taipei have ramped up, as she and her government reject China's claim to the island.

Her deputy, Vice President Lai, won the island's January presidential election despite warnings from Beijing that he would cause "war and decline" for Taiwan.

The latest sorties come a day after Manila summoned a senior Chinese envoy to protest against a water cannon incident that damaged two Philippine vessels during a patrol in the South China Sea.

A coast guard vessel and another government boat were damaged in the April 30 incident near the disputed Scarborough Shoal, according to the Philippines' foreign ministry.

Manila and Beijing have a long history of territorial disputes in the South China Sea, and the neighbours have been involved in several maritime incidents in recent months as they assert their rival claims in the strategic waterway.

The row comes as the United States and the Philippines conduct joint military exercises, including near the potential flashpoints of the South China Sea and the Taiwan Strait.

The joint drills involve a simulation of retaking enemy-occupied islands in areas facing Taiwan.