Chinese fighter jets briefly entered Taiwan's airspace yesterday, forcing the island to scramble its own, Taipei said shortly after announcing plans for its largest annual live-fire military drill.

The Taiwanese defense ministry said it broadcast warnings and "took active responses to dispel" multiple Chinese Su-30 fighters to the southwest of the island.

"The military is fully monitoring sea and air conditions around the Taiwan Strait and takes active responsive measures to defend our territorial safety," it said.

The incursion came as the ministry announced that the "Han Kuang" live-fire drill would be held next month, including computer simulations and an exercise to defend against forces landing on the island.

China has ramped up fighter flights and warship crossings near Taiwan or through the Taiwan Strait since President Tsai Ing-wen was first elected in 2016, as she has refused to acknowledge that the island is part of "one China".

It was the first major incursion since Tsai's landslide reelection in January.

Meanwhile, the speaker of the Czech upper house of parliament is to travel to Taiwan with a trade mission at the end of August, potentially further souring his country's relations with China.

The Czech Republic adheres to the "one China" policy, but unofficial ties with Taiwan exist, mainly in business and science.

Milos Vystrcil's decision follows a plan to visit Taipei by his predecessor as Senate speaker, Jaroslav Kubera.

Kubera died in January before he could make the trip, but was under pressure from China and the Czech presidency to drop the idea.

Vystrcil said yesterday he was motivated by business development and the country's tradition of human rights policies.

"We will either stick to our principles or count pennies. I am leaning toward keeping our values and principles," he said.

The incursion of Chinese Su-30 fighter jets came after Taiwan announced live-fire drill. AP

Taiwan warns off China fighter jets