Taiwan scrambled its jets and navy ships on Wednesday (11 January) as a group of Chinese warships led by Beijing's sole aircraft carrier sailed north through the Taiwan Strait.
The move is the latest rumbling of heightened tensions between the two countries in a long-running dispute over the South China Sea.
China's Soviet-built Liaoning aircraft carrier had been returning from carrying out exercises in the area, but had not trespassed in Taiwan's territorial waters.
However, the carrier had entered Taiwan's air defence identification zone (ADIZ) in the southwest, the country's defence ministry said in a statement seen by Reuters.
As a result, Taiwan scrambled jets and navy ships to "surveil and control" the passage of the Chinese ships through the narrow body of water separating Taiwan and China.
"We have full grasp of its movements," Taiwan defense ministry spokesman Chen Chung-chi said.
China has said its aircraft carrier was on exercises to test weapons in the South China Sea. However, its movements had complied with international law.
"These latest drills provide our first insights into how China will likely be using their aircraft carrier in the near future," Eric Wertheim, author of Combat Fleets of the World, told the US Naval Institute News, according to the Associated Press (AP).
"Rather than extended power projection in far-off waters, the Chinese appear more likely to use the carrier, at least initially, as a demonstration of regional muscle – sending a message that they are willing to back up talk, policy, or rhetoric with a show of strength."
According to Reuters, China distrusts Taiwan President Tsai Ing-wen and has stepped up pressure on her following a protocol-breaking, congratulatory telephone call between her and US President-elect Donald Trump.
Beijing suspects Tsai wants to push for the island's formal independence, a red line for the mainland, which has never renounced the use of force to bring what it deems a renegade province under its control. Tsai says she wants to maintain peace with China.