China has more than 50 navy and other official vessels operating in a wide swath of sea stretching from southern Japan down to Taiwan and off the Philippines, a senior Taiwan official said, calling the threat level "obvious".
Taiwan, which China views as its own territory, is stepping up efforts to issue details and maps depicting locations where Chinese warships and coast guard vessels operate.
"We're staying vigilant about their activities," said Joseph Wu, the secretary-general of Taiwan's National Security Council. "The simultaneous threat to Taiwan, Japan and the Philippines is obvious."
Wednesday's remarks accompanied a map he posted on social media showing the locations of 53 ships, 34 of them navy 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, according to the map.
Wu published a similar map on social media in May.
On Thursday, Zhang Xiaogang, a Chinese defence ministry spokesperson, said the Liaoning carrier's training in the western Pacific was an annual routine to test long-range, open-ocean combat capabilities and was not directed at any particular country.
The defence ministries of the Philippines and Japan did not immediately respond to requests for comment.
On Wednesday, 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.
This month, 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. It has been upset by Japanese support for Taiwan, while embroiled in an increasingly bitter standoff with Manila in the South China Sea.
"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 told reporters at parliament in Taipei on Thursday.
A senior Taiwan security official briefed on the matter said one thing to watch would be whether the Liaoning carrier group continues north towards Japan after drills in the Philippine Sea.
"If it keeps moving north, that would suggest a stronger intent to put pressure on Japan's defence posture," the official said.
China has never renounced the use of force to bring Taiwan under its control, though it says it would prefer "peaceful reunification".
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.
He made the comments at a forum in Hawaii on Tuesday, it added.
Taiwan was making efforts to build its own deterrence capabilities, Koo said when asked about Clark's remarks.
"China has never abandoned the use of force to annex Taiwan," he added.
China recognises no separate sovereignty for Taiwan, whose government says only the island's people can decide their future and that Beijing has no right to claim it.
(Reporting by Ben Blanchard and Yimou Lee; Additional reporting by Karen Lema in Manila, Tim Kelly in Tokyo and Joe Cash in Beijing; Editing by Clarence Fernandez, Lincoln Feast and Thomas Derpinghaus)