Hundreds of Taiwanese military reservists carried out training exercises on Monday after the island's president called for "unity" as the Ukraine war rattles nerves over the threat of invasion from China.

Taiwan last year stepped up its training regime for reservists as tensions rise with Beijing, which sees the self-ruled island as part of its territory to be seized one day, by force if necessary.

About 400 personnel took part in target practice Monday in a programme designed to boost their combat readiness. Their training kicked off earlier this month and simulates defending a beach near the capital Taipei.

It comes as Taipei keeps a close watch on Russia's invasion of Ukraine, with President Tsai Ing-wen appearing in front of the reservists on Saturday stressing the need for unity in defending the island.

"The recent situation in Ukraine once again proves that the protection of the country, in addition to international solidarity and assistance, depends on the unity of the people," she said in a speech while dressed in military fatigues and body armour.

Major General Chen Chung-chi, director of Taiwan's 6th Army Command, stressed the importance of reservists in addition to full-time troops.

"The security of the whole country does not just depend on the soldiers," he told AFP on Monday.

Taiwan President Tsai Ing-wen (R) inspects a training exercise for reservists at a military base in Taoyuan
Taiwan President Tsai Ing-wen (R) inspects a training exercise for reservists at a military base in Taoyuan AFP / Sam Yeh

"In Ukraine, we see soldiers in the battlefield, and some men... who go to battle after sending their wives and children to safety."

"Military power is limited but the power of the people is unlimited."

Reservist Shi Hui-bin said the immersion training kept him prepared and up to date with current military tactics.

"When the time comes, I will know what to do," he told reporters after a round of shooting practice.

China's sabre-rattling against Taiwan has ramped up since Tsai took office in 2016 as she rejects Beijing's view that Taiwan is part of "one China".

Chinese warplanes have increasingly breached Taiwan's air defence zone and Moscow sides with Beijing that Taiwan is "an inalienable part" of China.

On Monday, Taiwan's Ministry of National Defence reported that 13 Chinese warplanes -- 12 of which were fighter jets -- entered Taiwan's air defence zone, the largest number of incursions this month.

The island has recently seen a massive spike in incursions, with the biggest single-day coming on October 4 when 56 Chinese warplanes entered the zone, according to an AFP database recording daily incursions.