Beijing, which views self-ruled Taiwan as its own territory to be seized one day, has stepped up military and political pressure on the island in recent years as relations deteriorate.

Taiwan on Monday detected China's Shandong carrier -- one of two in Beijing's fleet -- around 60 nautical miles (111 kilometres) southeast of the island as it sailed into the Western Pacific.

Chinese aircraft including fighters and drones were then tracked around the island from Wednesday morning, Taipei's defence ministry said.

Some fighters "passed through the Bashi Channel to the Western Pacific to conduct joint sea and air training with the Shandong aircraft carrier", the ministry said in a statement.

Taipei's Ministry of Defence on Wednesday released an undated photo showing the Shandong being monitored by a Taiwanese Keelung class warship.

"The armed forces have monitored the situation and tasked air patrol aircraft, Navy vessels, and land-based missile systems to respond to these activities," it said.

Beijing is yet to comment on the drills.

But the country's Eastern Theatre Command -- which organises drills around Taiwan -- said Wednesday an "aviation unit" had carried out training "recently", with a range of "thousands of kilometres". It did not mention the island.

- 'High alert' -

On Saturday, China said its troops were "on constant high alert" after two ships belonging to the United States and Canada sailed through the Taiwan Strait.

The US Navy said the ships were the Arleigh Burke-class guided-missile destroyer USS Ralph Johnson and HMCS Ottawa, and that the transit "demonstrates the commitment of the United States and our allies and partners to a free and open Indo-Pacific".

The United States and Western allies have increased "freedom of navigation" crossings of both the Taiwan Strait and the disputed South China Sea to reinforce that both are international waterways, angering Beijing.

In April, Beijing conducted military exercises to simulate the encirclement of the island in April after Tsai met US House Speaker Kevin McCarthy in California.