Relations between Taipei and Beijing have deteriorated since President Tsai Ing-wen was elected in 2016, as her government refuses to acknowledge that Taiwan is part of "one China".

Live-fire drills began Monday with troops simulating surprise air and coastal assaults to reflect increased military threats from China, which sees Taiwan as a renegade province to be brought back into the fold -- by force if necessary.

Tsai watched Thursday's session of the ongoing "Han Kuang" (Han Glory) exercise involving 4,100 soldiers, attack helicopters and fighter jets from an air base in Taichung.

Thursday's scenario simulated the enemy bombing of an airfield and a paratrooper attack, with air and ground troops deployed to take back the base.

An F-16 fighter flew overhead and deployed flares in a defensive move against heat-seeking missiles. Special operations troops were seen moving to secure a building.

"I have seen our troops' capabilities and I have faith that our troops can achieve the goal of 'solid defence and multiple deterrence'," Tsai said.

China held its own live-fire drills in April in the Taiwan Strait -- the narrow waterway separating the Chinese mainland from Taiwan -- following weeks of air and naval manoeuvres in the area.

Beijing has also stepped up diplomatic pressure on Taipei, luring four countries to switch allegiance from Taiwan to China since Tsai took office.

China has been incensed by a recent warming in relations between Taiwan and the United States, which remains the island's most powerful ally and arms supplier even though it has no official diplomatic ties.

President Donald Trump recently signed a symbolic bill paving the way for mutual visits by high-level officials and Washington gave long-awaited approval for a licence necessary to sell submarine technology to Taiwan.

A defence spending bill currently before congress in Washington calls on the US military to participate in Taiwan's drills, including the annual Han Kuang exercise.

"We are optimistic about all exchanges with the US as long as it's about national security, and regional peace and stability," defence ministry spokesman Chen Chung-chi said when asked to comment on American participation in Taiwan's drills.

On Monday, the pilot of an F-16 jet involved in the drills was killed after crashing into a mountain in northern Taiwan.

The cause of the incident was under investigation.