H-6K bombers, early warning aircraft, reconnaissance planes and several types of fighter jets took off from multiple airports for "combat drills", the air force said in a statement on its official microblog.

The planes flew over Bashi Strait, south of Taiwan and the Miyako Strait, near Japan's Okinawa Island, it said.

The air force said its H-6K bombers have completed several drills that involved circling Taiwan since April 18 "to strengthen its capacity to safeguard national sovereignty and territorial integrity".

"The series of operations we are carrying out is directed against Taiwan independence forces and activities in the island," defence ministry spokesman Wu Qian told a monthly press conference.

"Their purpose is to prevent that the Taiwan independence forces' plot damages the welfare of the Taiwanese people. If the independence forces continue to wantonly take rash actions, we will take further actions," Wu said.

China sees the democratically-governed island -- which has never formally declared independence from the mainland -- as a renegade part of its territory to be brought back into the fold, and has not ruled out reunification by force.

Taipei has accused Beijing of "sabre rattling" and trying to stoke regional tensions with its recent drills.

Taiwan announced on Tuesday that it will practise thwarting a Chinese "invasion" in annual live fire drills in June by simulating surprise coastal assaults.

Chinese H-6K bombers and spy planes had previously flown around Taiwan last week.

Chinese combat helicopters conducted live-fire drills with missiles off southeast China on April 18, state media said last week without confirming whether the exercises took place in the sensitive Taiwan Strait.

Beijing has stepped up military patrols around Taiwan and used diplomatic pressure to isolate it internationally since President Tsai Ing-wen, of the traditionally pro-independence Democratic Progressive Party, took office in 2016.

Beijing's sole aircraft carrier and two destroyers crossed waters south of Taiwan Saturday and carried out "offensive and defensive" drills in the Pacific, China's navy said.