Taiwan reported a Chinese aircraft carrier group sailing to the island's south on Sunday, as China's military put out a video saying it was "prepared for battle" amid concerns in Taipei about the possibility of a new round of Chinese war games.
China, which views democratically governed Taiwan as its own territory, detests its president Lai Ching-te as a "separatist", and the Chinese military routinely operates around the island.
Last week at his keynote national day speech, Lai said the People's Republic of China had no right to represent Taiwan, but that the island was willing to work with Beijing to combat challenges like climate change, striking both a firm and conciliatory tone, but drawing anger from China.
Taiwan's defence ministry said in a statement that a Chinese navy group led by the carrier the Liaoning had entered waters near the Bashi Channel, which connects the South China Sea and the Pacific and separates Taiwan from the Philippines. It said the carrier group was expected to enter the Western Pacific.
Taiwan's armed forces are keeping a close watch on developments and "exercising an appropriate vigilance and response", the ministry added, without elaborating.
Security sources in Taiwan had said before Lai's address that his speech could prompt new Chinese war games, last held by the country in May in what Beijing said was "punishment" for Lai's inauguration speech that month.
Earlier on Sunday, the People's Liberation Army's Eastern Theatre Command, which has responsibility for an area that includes Taiwan, put out a propaganda video on its social media accounts entitled "fully prepared and biding ones time before battle".
It showed fighter jets and warships operating together, mobile missile launchers being moving into place and amphibious assault vehicles, with a small map of Taiwan included in one of the Chinese characters that make up the video's title.
China has not ruled out using force to bring Taiwan under its control.
China's defence ministry did not answer calls outside of office hours on Sunday. China's Taiwan Affairs Office did not immediately respond to a request for comment.
A Taiwan security official, speaking on condition of anonymity given the sensitivity of the matter, told Reuters they were continuing to watch the situation around the island, as well as Chinese media comments about Lai's national day speech.
Chinese media has carried several commentaries and stories since Lai's Thursday speech denouncing the contents as "confrontational" and harmful.
Some comments on Chinese social media about the military's "battle preparation" video called for "Taiwan to return to the motherland" and "national reunification".
A second security source in Taiwan, familiar with intelligence assessments, said while it was still possible China, wary of creating a crisis over Taiwan so soon ahead of next month's U.S. election, might keep its reaction to angry words, there remained the possibility of more war games.
China is in the middle of its annual drills season, and its military could just "hang a name" on those exercises and turn them into war games specifically targeting Taiwan, the official, also speaking anonymously, told Reuters.
China's commerce ministry on Saturday threatened Taiwan with more trade sanctions, in what the government views as Chinese economic coercion.
Lai and his government reject Beijing's sovereignty claims, saying only Taiwan's people can decide their future. Lai has repeatedly offered talks with Beijing but been rebuffed.
