Taiwan said it was "on alert" as it detected a Chinese aircraft carrier group to its south on Sunday, days after the United States warned Beijing against taking "provocative" actions on the self-ruled island.
US State Secretary Antony Blinken warned China on Friday against taking action in response to a speech by Taiwanese President Lai Ching-te during the island's National Day celebrations.
China has ramped up military activity around Taiwan in recent years, sending in warplanes and other military aircraft while Chinese ships maintain a near-constant presence around its waters.
Taiwan's defence ministry said Sunday that a Chinese Liaoning aircraft carrier group had entered the Bashi Channel, a waterway that separates the island from the Philippines, "and is likely to proceed into the western Pacific".
"The Taiwanese military is employing joint intelligence, surveillance, and reconnaissance systems to closely monitor related activities and remains on alert, prepared to respond as necessary," it said in a statement.
China's military meanwhile released a video on Sunday saying it was "prepared for battle", with a small map of Taiwan included in its title.
The video, posted on the People's Liberation Army Eastern Theater Command's social media channels, shows missiles, jets, helicopters, and warships. China's military was "ready for battle at any time" the post added.
Taiwan and US officials had warned of possible Chinese military drills in response to Lai's speech.
The United States is Taiwan's most important backer and biggest supplier of weapons, but does not hold formal diplomatic relations with Taipei.
'Resist annexation'
Lai, who took office in May, has been more outspoken than his predecessor Tsai Ing-wen in defending Taiwan's sovereignty, angering Beijing, which calls him a "separatist".
In his speech on Thursday, Lai vowed to "resist annexation" of the island, and insisted Beijing and Taipei were "not subordinate to each other".
China warned after the speech that Lai's "provocations" would result in "disaster" for the people of Taiwan.
Taiwan's National Day on Thursday marked the 113th anniversary of the toppling of China's Qing dynasty and the subsequent founding of the Republic of China — which remains Taiwan's official name.
The current dispute between China and Taiwan dates back to a civil war in which the nationalist forces of Chiang Kai-shek were defeated by Mao Zedong's communist fighters and fled to Taiwan in 1949.
Lai's Democratic Progressive Party has long defended the sovereignty and democracy of Taiwan, which has its own government, military and currency.
Beijing has sought to erase Taipei from the international stage, blocking it from global forums and poaching its diplomatic allies.
China has held three rounds of large-scale war games in the past two years, deploying aircraft and ships to encircle the island.
Taiwan's defence ministry said Sunday that 11 Chinese military aircraft and eight navy vessels were detected around the island in the 24 hours to 6:00 am.
