Taiwan's defence minister called on youths to join the army Monday after Chinese military aircraft came near the island over the weekend during a drill for the second time in the past month.

Saturday's incident saw more than 10 Chinese aircraft pass through the Miyako Strait in Japan's Okinawa chain as well as the Bashi Channel to the south of Taiwan, according to the defence ministry.

Officials gave no further detail on how close the planes had come to the island, but they did not enter Taiwan's airspace.

It comes as tense cross-strait relations have been further rattled by United States president-elect Donald Trump's unprecedented phone call with Taiwan's Beijing-sceptic president Tsai Ing-wen, and his suggestion Sunday that he could drop Washington's "one China" policy which guides relations with self-ruling Taiwan.

Taiwan's defence minister Feng Shih-kuan called the timing of China's air drill a coincidence, but warned the island is still at risk of military threat.

"China's actions must have political significance," Feng told reporters Monday.

The defence ministry does not always make such incidents public, but wanted to raise awareness of "threats" to the island, said Feng.

"We want to let our people know that we still face threats from our enemies," he said.

Feng used the opportunity to urge youngsters to sign up for Taiwan's military, which consists of around 200,000 troops, a fraction of China's 2.3 million-strong army.

"We hope aspiring young people can join the military force under the recruitment system and defend our country," Feng said.

China poses the main military threat to Taiwan, which Beijing sees as part of its territory to be brought into its fold -- by force if necessary.

It has 1,500 missiles aimed at the island, according to Taiwan's defence ministry.

Taiwan has been struggling to end one-year compulsory conscription and make its military a voluntary service, delaying its target date several times due to insufficient recruitment.

An earlier plan to make the forces voluntary by 2017 was pushed back again in August. Feng said that the defence ministry would halt conscription from 2018.

Saturday's drill also prompted a spat between Beijing and Tokyo after China's defence ministry alleged Japanese fighter jets obstructed its aircraft during the excercise, launching "decoy flares."

Tokyo has denied the accusation.