Beijing has not ruled out using force to bring Taiwan under its control and Monday's drills represent its fourth round of large-scale war games in the past two years.

China's drills come days after US Secretary of State Antony Blinken warned Beijing against taking action in response to a speech by Taiwanese President Lai Ching-te during the island's National Day celebrations.

Lai, who took office in May, has been more outspoken than his predecessor Tsai Ing-wen in defending Taiwan's sovereignty, angering Beijing, which calls him a "separatist".

Taiwan condemned the latest exercises as "irrational and provocative" and said it has dispatched "appropriate forces" in response.

AFP journalists near the Hsinchu air force base, in the north of Taiwan, saw four fighter jets take off on Monday.

The drills, dubbed Joint Sword-2024B, "test the joint operations capabilities of the theater command's troops", Beijing said.

They are taking place in "areas to the north, south and east of Taiwan Island," said Captain Li Xi, spokesman for the Chinese military's Eastern Theater Command.

The drills are "focusing on subjects of sea-air combat-readiness patrol, blockade on key ports and areas", Li said.

They also practised an "assault on maritime and ground targets" and "joint seizure of comprehensive superiority".

China's coast guard was also dispatched to conduct "inspections" around the island.

A diagram released by the coast guard showed four fleets encircling Taiwan and moving in an anticlockwise direction around the island.

Taiwan said it had detected "convoys" of China coast guard ships "in our northern, southwest and eastern waters".

China has ramped up military activity around Taiwan in recent years, sending in warplanes and other military aircraft while its ships maintain a near-constant presence around the island's waters.

Taiwan said Sunday it had detected a Chinese aircraft carrier group to its south in the Bashi Channel, a waterway that separates the island from the Philippines, that appeared to be heading towards the western Pacific.

"In the face of enemy threats, all officers and soldiers of the country are in full readiness," Taiwan's defence ministry said Monday.

"We are determined and confident to ensure national defence security."

- 'Provocations' -

In his speech on Thursday, Lai vowed to "resist annexation" of the island, and insisted Beijing and Taipei were "not subordinate to each other".

China warned after the speech that Lai's "provocations" would result in "disaster" for the people of Taiwan.

Beijing on Monday said the drills were "a legitimate and necessary operation for safeguarding state sovereignty and national unity".

Beijing's state broadcaster CCTV released a video warning: "the greater the provocation, the tighter the reins".

The current dispute between China and Taiwan dates back to a civil war in which the nationalist forces of Chiang Kai-shek were defeated by Mao Zedong's communist fighters and fled to Taiwan in 1949.

Lai's Democratic Progressive Party has long defended the sovereignty and democracy of Taiwan, which has its own government, military and currency.

Beijing has sought to erase Taipei from the international stage, blocking it from global forums and poaching its diplomatic allies.

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STERN GROEP