The carrier Liaoning, accompanied by two destroyers, two frigates and a combat support ship, was spotted by Japan as it passed through the Miyako Strait on Saturday evening

The carrier is the only ship of its kind still operational in the region after USS Theodore Roosevelt and USS Ronald Reagan were forced to dock after crew were hit by Covid-19.

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Taiwan scrambled warships on Saturday night to monitor the movements of a mainland Chinese carrier strike group after it was spotted by Japan heading towards the western Pacific.

The fleet, led by China's first aircraft carrier, the Liaoning, was seen passing through the Miyako Strait near Okinawa, and then turning south, the Japanese Ministry of Defence said.

Although the precise location or heading of the group was unknown, the Taiwanese navy scrambled ships from the northeastern port of Suao to monitor the situation, the island's defence ministry said.

The Miyako Strait is about 330km (205 miles) due east of the northernmost tip of Taiwan.

"We have conducted reconnaissance and monitoring over the sea and air space around Taiwan," ministry spokesman Shih Shun-wen said.

To the Taiwanese public, he added: "Please be reassured."

As tensions continue to simmer between Beijing and Taipei, the People's Liberation Army (PLA) has increased its activities around the self-ruled island, which the mainland regards as part of its territory awaiting reunification.

On Thursday, an H-6 bomber, J-11 fighter and KJ-500 reconnaissance plane from the PLA Air Force flew over southwestern Taiwan and on to the western Pacific where they followed a US RC-135U electronic reconnaissance aircraft.

The Liaoning was escorted on Saturday by two type 052D guided-missile destroyers — the Xining and Guiyang — two type 054A guided-missile frigates — the Zaozhuang and Rizhao — and a type 901 combat support ship, the Hulunhu.

The Liaoning is currently the only aircraft carrier active in the western Pacific after the Covid-19 pandemic hit the US Navy and left a vacuum in the region.

The USS Theodore Roosevelt carrier had been deployed in the region but was forced to dock in Guam after hundreds of its crew contracted the coronavirus. The ship's captain was later sacked for disclosing information about the incident.

A second US aircraft carrier, the USS Ronald Reagan, is currently docked in Yokosuka, Japan, after members of its crew also tested positive for Covid-19.

While the PLA navy has not issued any reports of its personnel being infected, in February, officers from the Shandong aircraft carrier dismissed rumours its crew had been infected, saying the ship was conducting training exercises as planned.

The Liaoning's last visit to the west Pacific was in June, when it was also supported by five other vessels. During the trip it approached Guam, a strategic base for US air and naval forces in the region, and sailed through the Taiwan Strait on its return home.

Taiwan's defence ministry said that also on Saturday evening, USS Barry-DDG 52, an Arleigh-Burke class guided-missile destroyer, sailed through the Taiwan Strait.

On Sunday, a US Navy EP-3E electronic reconnaissance aircraft flew past the south of the island en route to the South China Sea, according to the military aircraft tracking Twitter account, Aircraft Spots.