China insists democratic Taiwan is part of its territory and has threatened to use force to bring the island under its control.

Beijing has increased the deployment of fighter jets and naval vessels around Taiwan in recent years to press its claim of sovereignty, which Taipei rejects.

The Chinese military said Tuesday the exercises were aimed at sending a "stern warning and forceful deterrence" to alleged separatists in Taiwan.

The drills "focus on sea-air combat-readiness patrols, joint seizure of comprehensive superiority, assault on maritime and ground targets, and blockade on key areas and sea lanes", said Senior Colonel Shi Yi, spokesperson of the Chinese military's Eastern Theater Command.

China's armed forces "close in on the Taiwan Island from multiple directions", he said, describing the move as "a legitimate and necessary action to safeguard China's sovereignty and national unity".

Taiwan President Lai Ching-te last month called China a "foreign hostile force" and proposed measures to combat Chinese espionage and infiltration.

The Chinese military's Eastern Theater Command -- which oversees operations along the Taiwan Strait -- shared a graphic with the title "closing in".

It showed ships and fighter jets surrounding the island, warning "Taiwan separatists" were "Courting Disaster Upon Themselves".

Another graphic shared by the military depicted Lai as an insect being roasted over an open fire.

- Potential flashpoint -

This week's drills are the biggest since February, when Taipei said that China staged a "live-fire" combat drill with aircraft and warships in an area about 40 nautical miles (74 kilometres) off the island's south.

Taiwan's military responded by sending forces to "monitor, alert and respond appropriately".

Beijing at the time rejected "pure hype" from Taiwan over what it called "routine training".

Taiwan is a potential flashpoint for a war between China and the United States, which is the island's most important backer and biggest arms supplier.

While the United States is legally bound to provide arms to Taiwan -- which Beijing opposes -- Washington has long maintained "strategic ambiguity" when it comes to whether it would deploy its military to defend it from a Chinese attack.

Last week, the island's deputy defence minister attended a ceremony in the United States unveiling the first F-16V fighter jet built for the island.

The entire production of the aircraft is expected to be completed next year and all jets are scheduled to fly back to Taiwan by the end of 2026.

The dispute between China and Taiwan dates back to 1949 when Chiang Kai-shek's Kuomintang nationalist forces fled to Taiwan after losing the Chinese civil war with Mao Zedong's communist fighters.

Communist China has never ruled Taiwan, where indigenous tribes have lived for thousands of years. The island was partly or totally ruled at various times by the Dutch, Spanish, China's Qing dynasty and Japan.