Taiwan's military has sent forces to keep watch on a Chinese naval formation led by the aircraft carrier Shandong sailing through the sensitive Taiwan Strait, Taiwan's defence ministry said on Thursday.

The Shandong participated in Chinese military drills around Taiwan in April, and again entered the Pacific last month.

The ministry said in a statement that the formation led by the Shandong entered the narrow Taiwan Strait on Wednesday afternoon sailing in a northerly direction but keeping to the Chinese side of the waterway's median line, an unofficial barrier between the two.

China says the Taiwan Strait is not an international waterway and that it alone has sovereignty there, which both Taiwan and the United States dispute. The United States frequently sends warships through the strait, most recently last week, that time accompanied by a Canadian frigate.

As of Thursday morning, the Chinese carrier group was continuing to sail northwards, Taiwan's defence ministry said. Taiwan has dispatched "appropriate" forces to keep watch, it added, without elaborating.

China's defence ministry did not immediately respond to a request for comment.

Japan's defence ministry said on Monday that the Shandong and other naval ships had sailed to the South China Sea after conducting landing drills in the Pacific Ocean for nine days.

The Shandong, commissioned in 2019, also sailed through the Taiwan Strait in June.

Taiwan has repeatedly complained of Chinese air force planes crossing the strait's median line.

China, which has never renounced the use of force to bring Taiwan under its control, has stepped up military activity near the democratically governed island, responding to what it calls "collusion" between Taiwan and the United States.

Taiwan's government strongly rejects Beijing's sovereignty claim.