Taiwan's annual war games this year will be as close as possible to actual combat, no longer just putting on a show to score points but aiming to simulate real fighting given a rapidly rising "enemy threat" from China, a senior official said.

China, which views democratically governed Taiwan as its territory, has been staging regular exercises around the island for four years to pressure Taipei to accept Beijing's claim of sovereignty, despite Taiwan's strong objections.

Taiwan starts its five-day Han Kuang exercises on July 22.

A senior Taiwan defence official, speaking on condition of anonymity to be able to speak more freely, said there was an urgent need to rethink how the drills were conducted.

"In recent years, the enemy threat has changed rapidly," the official said. "Our defence combat plan must also be continuously revised on a rolling basis, and the urgency of comprehensive combat training is becoming more and more important."

Elements that were mostly for show, like rehearsal drills, have been cancelled, while this year there will be nighttime exercises and, unusually, the capital Taipei will be included too, the official said.

"It's not about scoring points," the official said. "We want the soldiers to wonder whether this is for real."

Things may go wrong, like vehicle breakdowns, and that is fine, the official added. "These are problems that may be faced in actual combat."

The exercises will be a continuous experience, the official said. "War does not distinguish between night and day."

China's defence ministry did not answer calls seeking comment about the exercises outside of office hours at the weekend. 

It has previously said it is futile for Taiwan to think it can use arms to prevent "reunification".

Announcing the drills in April, Taiwan's defence ministry said the war games would practice "kill" zones at sea to break a blockade and simulate a scenario where China suddenly turns one of its regular drills around the island into an attack.

"Only with real-time, on-the-ground verification can we truly understand the capabilities and limitations of our troops," the official said.

China held two days of its own war games around the island shortly after President Lai Ching-te took office last month, saying it was "punishment" for his inauguration speech, which Beijing denounced as being full of separatist content.

But China has also been using grey zone warfare against Taiwan, wielding irregular tactics to exhaust a foe by keeping them continually on alert without resorting to open combat. 

This includes sending balloons over the island and almost daily air force missions into the skies near Taiwan.

China has never renounced the use of force to bring Taiwan under its control. Lai, who says only the Taiwanese people can decide their future, has repeatedly offered talks but been rebuffed.

The official declined to comment on which parts of the war games Lai would attend, as is customary for the president as commander-in-chief, or whether there would be U.S. observers.