Taiwanese officials have raised the alarm after more than 50 Chinese navy and other official vessels were reportedly sighted in waters near the self-governed island.
Joseph Wu, the secretary general of Taiwan's National Security Council, said the threat level from China's naval activity in waters stretching from southern Japan down to Taiwan and off the Philippines was "obvious".
"We're staying vigilant about their activities," Mr Wu said. "The simultaneous threat to Taiwan, Japan and the Philippines is obvious."
He shared a map on X showing the locations of 53 vessels, out of which 34 were warships, including the aircraft carrier Liaoning.
The carrier and its accompanying battle group were positioned to the east of the Philippines, with other formations off Taiwan's east and southeast, along with three off the southern coast of Japan, as per the map.
"We are not happy to see any attempt to project deterrence that could undermine peace and stability in the Indo-Pacific region," Taiwan defence minister Wellington Koo said on Thursday.
Beijing, which claims Taiwan as its own territory, conducts elaborate war games involving aircraft and warships around the island, which analysts say blurs the line between routine military training and stage-setting for an attack.
China has never renounced the use of force to bring Taiwan under its control, though says it would prefer "peaceful reunification".
Japan's defence ministry said it had tracked three Chinese warships and a Coast Guard ship a day earlier as they passed through the narrow Osumi Strait off Kyushu island and into the Pacific.
China's defence ministry said the Liaoning was engaged in a routine training exercise not directed at any specific country.
China's ties with both Japan and the Philippines have tanked in recent months amid Beijing's growing aggression in the Pacific waters.
China has been upset by renewed Japanese support for Taiwan, while embroiled in an increasingly bitter stand-off with Manila in the South China Sea.
China views almost all of the South China Sea as its own territory, despite overlapping claims by Brunei, Malaysia, the Philippines, Taiwan and Vietnam.
The Taiwanese defence minister told reporters in Taipei that in addition to intelligence exchanges with partners, his ministry was "maintaining appropriate awareness" of Chinese military warship activity.
US Army forces in the Pacific have prepared the Indo-Pacific theatre under the assumption that China could move on Taiwan as early as next year, the US military newspaper the Stars and Stripes quoted their commander, Ronald Clark, as saying.
Taiwan was making efforts to build its own deterrence capabilities, Mr Koo said when asked about Mr Clark's remarks. "China has never abandoned the use of force to annex Taiwan," he added.
Last week, Japan said it spotted Chinese military aircraft, spy drones and warships as Tokyo and Washington conducted drills.
Earlier this month, China said it had sent forces to watch the USS Charleston, which it claimed "illegally intruded" waters adjacent to Sabina Shoal in the Spratly Islands without Chinese government approval.
A US Navy 7th Fleet spokesperson said the USS Charleston conducted routine operations in international waters consistent with international law.
The Philippine military said the US ship "did not trespass into 'Chinese territory'," adding that no nation had the authority to require prior permission for "lawful transit through international waters."
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