The Han Kuang exercises, which started Monday, are held every year across Taiwan to train its armed forces as China ramps up military pressure on the democratic island, which Beijing claims as part of its own territory.

But as Gaemi -- currently categorised as a medium-strength typhoon -- edged closer to Taiwan Tuesday, the island's northern regions started seeing heavy rains, with the Central Weather Administration predicting landfall by late Wednesday.

Speaking to reporters on Tuesday at an airbase in eastern Hualien, defence ministry spokesman Sun Li-fang said the military will make "flexible adjustments based on the weather conditions in our exercise missions".

"At present, the impact of the typhoon is more obvious in the eastern region and we will make some adjustments to some sea and air exercises due to the typhoon situation," he said.

The Central Weather Administration issued sea and land warnings on Tuesday morning, with Gaemi packing sustained wind speeds of 155 kilometres (96 miles) per hour as it headed towards the island's northeastern coast.

Taiwan experiences frequent tropical storms from May to November.

Dressed in military fatigues, President Lai Ching-te looked on as soldiers went through a simulated mass casualty rescue exercise at the Hualien airforce base.

"Proud of our troops' unwavering resolve... As guardians of democracy, your efforts are vital for national security & demonstrate our commitment to self-defense," he said in a post on social media platform X.

-'Seek immediate shelter' -

The war games this year are a departure from previous iterations, discarding exercises that were "more for demonstration purposes" and opting instead to more realistically simulate an attack from China, the defence ministry had said.

The exercises will also work on decentralising the command structure, while conducting drills around key infrastructure points -- like Taiwan's sea ports, major bridges, and airports.

By afternoon, Lai arrived in New Taipei City at a port to oversee an elaborate simulation of various emergency situations as part of the annual civilian defence drills -- which run concurrently with Han Kuang.

Out of his military uniform and donning a tie, the president watched a scenario whereby Chinese missiles had hit the port and its surroundings -- according to an announcer narrating over loudspeaker -- which prompted workers to evacuate civilians.

Calling Taipei Port a "critical infrastructure", Lai said the scenarios "not only included the risks that the port may face at normal times, but also integrated large-scale compound disaster drills".

In the capital Taipei, air raid sirens blared and staff at a train station ushered passengers out, while some people sheltering in a parking lot were told to crouch down.

Taipei residents also received an automated text message that said "(Air Defense Drill) Incoming missile/rocket threat. Seek immediate shelter."

Lai, who is a staunch defender of Taiwan's democracy, is regarded as a "dangerous separatist" by China.

Three days after he was sworn into office in May, China launched war games simulating an encirclement of the island as "punishment" for his inauguration speech, which Beijing said was a "confession of Taiwan independence".

China has said it would never renounce the use of force to bring Taiwan under its control, and maintains a near-daily military presence around the island by sending in warplanes, navy vessels and drones.