Taiwan said Monday it was closely monitoring the movements of China's sole aircraft carrier and five other warships, which earlier passed south of the island on an exercise held amid worsening cross-strait relations.

The Liaoning and five escorts sailed 20 nautical miles outside Taiwan's air defence identification zone (ADIZ) in the Bashi Channel between Taiwan and the Philippines on Sunday, the defence ministry said.

The ships continued sailing southwest after passing 90 nautical miles (150 kilometres) to the south of Taiwan's southernmost point Eluanbi Monday morning. They later travelled to the southeast of the Dongsha Islands in the South China Sea, the ministry added.

"The military has been on guard and fully monitoring the Liaoning. We urge the public to rest assured," it said.

Taiwanese media said an unspecified number of F-16 fighter jets and warships were deployed in Taiwan's ADIZ to closely watch the Chinese warships. The ministry declined to comment.

Japan's defence ministry said earlier that eight Chinese vessels, including the carrier and three destroyers, were spotted by one of its ships in the central part of the East China Sea on Saturday afternoon.

Chinese media has reported that the aircraft carrier was headed for the Pacific on exercise for the first time.

The navy drills are seen as a show of strength by Beijing at a time of rising tensions with Taiwan and the United States following a protocol-breaking telephone conversation between Taiwanese President Tsai Ing-wen and US President-elect Donald Trump.

It was the latest in a series of recent exercises staged by China, after its military aircraft passed near Taiwan on December 10 for the second time in a month.

Taiwan's defence minister Feng Shih-kuan has called the timing of China's air exercises a coincidence, but warned the island still faces a military threat.

China views self-ruling Taiwan as part of its territory awaiting unification, by force if necessary, even though the two sides split in 1949 after a civil war.

China aircraft carrier to lead Pacific drills for first time
Beijing (AFP) Dec 25, 2016 - China's navy sent its sole aircraft carrier into the Pacific for the first time, state media reported -- a move likely to ratchet up regional tensions.

The duration of the drill and the route of the flotilla were not known. But the Soviet-made carrier is based in the northeastern city of Dalian, suggesting the fleet would enter the Pacific through a disputed island chain between Taiwan and Japan.

"A Chinese navy formation, including the aircraft carrier Liaoning, headed towards the West Pacific on Saturday for scheduled blue-water training," Xinhua said Saturday, citing China's navy spokesperson Liang Yang.

Japan's defence ministry confirmed eight Chinese vessels, including the carrier and three destroyers, had been spotted by one of its ships in the central part of the East China Sea on Saturday afternoon.

In recent days the Liaoning has been involved in exercises in the Yellow Sea, with J-15 fighter jets taking off from it and conducting air refuelling and combat drills, Xinhua said.

Earlier in the month the Liaoning led large-scale exercises in the Bohai Sea that included live ammunition for the first time.

State broadcaster CCTV in mid-December showed images of fighter jets taking off from the aircraft carrier, with targets exploding into flames and missiles releasing long trails of smoke.

Tokyo controls the string of uninhabited islands known as the Senkakus in Japan and the Diaoyus in China that are also claimed by Beijing and Taipei.

The Chinese navy drills are seen as a show of strength by Beijing at a time of rising tensions with Taiwan and the United States following a protocol-breaking telephone conversation between Taiwanese President Tsai Ing-wen and US President-elect Donald Trump.

China views Taiwan as a renegade province and fiercely opposes diplomatic recognition of it as a country.

Beijing is seeking to modernise and upgrade its military both to protect its borders and project power into regions such as the South China Sea, a resource-rich strategic waterway where it has disputes with several neighbours.

Last Tuesday the Chinese navy returned a US underwater probe it had seized in the South China Sea, where competing territorial claims have heightened tensions in the region.

In December 2015, the ministry of defence announced plans for Beijing to build its second aircraft carrier.