Beijing insists democratic Taiwan is part of its territory and has never renounced the use of force to bring the self-ruled island under its control.

The Han Kuang exercises, which the defence ministry said would be held from July 9-18, are conducted every year across Taiwan to train its armed forces as China ramps up military pressure on the island.

Defence Minister Wellington Koo told parliament as many as 22,000 reservists would be called up to take part in the exercises, up from 14,647 last year.

"Our main objective is to verify how much time it takes for a reserve brigade to regain full combat capability after being called up," Koo said.

Taiwan maintains a standing call-up system to train its reservists. This year the mobilisation will be expanded as part of the annual Han Kuang military drills.

The defence ministry also said the annual drills would be extended to 10 days and nine nights, compared with five days and four nights last year.

Koo said the most significant change would be the inclusion of "grey zone harassment" scenarios, simulating a military escalation based on "regional developments".

Taiwan accuses China of using "grey-zone" tactics -- actions that fall short of an act of war -- to weaken its defences.

Beijing regularly deploys fighter jets, warships and coast guard ships near Taiwan, and has held several major military exercises around the island in recent years.

The Taiwan reservists called up will undergo a full 14-day training programme, 10 days of which will be dedicated to participation in the drills.

In March, Taiwan's defence ministry said it would simulate possible scenarios for a Chinese invasion in 2027 during Han Kuang drills.

Officials in the United States -- Taipei's main backer and biggest arms supplier -- have previously cited 2027 as a possible timeline for a Chinese invasion of Taiwan.