Taiwan told China on Monday to stop its "destructive unilateral actions" after more than 100 Chinese warplanes and nine navy ships were detected in areas around the self-ruled island.
Beijing claims Taiwan as its own territory to be seized one day, by force if necessary, and has ramped up diplomatic and military pressure on Taipei in recent years.
Taiwan's defence ministry described the number of warplanes detected in 24 hours as a "recent high", while Beijing has so far refrained from issuing any official comment on the sorties.
"Between the morning of September 17th to 18th, the Ministry of National Defence had detected a total of 103 Chinese aircraft which was a recent high and has posed severe challenges to the security across the Taiwan Strait and in the region," it said in a statement.
Beijing's "continued military harassment can easily lead to a sharp escalation in tension and worsen regional security," the ministry said, as it called on China to "immediately stop such destructive unilateral actions."
Of the total number of warplanes detected, 40 crossed the so-called median line of the Taiwan Strait that separates the island from China, and entered its southwest and southeast air defence identification zone (ADIZ), the statement said.
'High alert'
Last week, Taipei also reported an increased number of incursions by Chinese warplanes and ships.
The uptick came as Beijing said its troops were on "high alert" after two ships belonging to the United States and Canada sailed through the Taiwan Strait.
Taiwan's defence ministry said 68 Chinese aircraft and 10 naval vessels were detected around the island between Wednesday morning and Thursday morning.
Some of those planes and warships were heading to an unspecified area of the Western Pacific to "conduct joint sea and air training" with China's Shandong aircraft carrier, the ministry said.
The Shandong, one of two operational aircraft carriers in the Chinese fleet, was detected last week around 60 nautical miles (110 kilometres) southeast of Taiwan heading into the Western Pacific, Taipei authorities said.
Japan's defence ministry also said last week its navy had detected six ships -- including frigates, destroyers, one fast combat support ship and the Shandong -- sailing through waters some 650 kilometres (400 miles) south of Miyakojima island, east of Taiwan.
It confirmed that jets and helicopters had been detected taking off and landing from the Shandong, though China has not commented officially on any drills being conducted in the Western Pacific.
'The same China'
Analysts said China could be flexing its muscles to counter US influence in the Asia-Pacific, as it leads multiple rounds of military drills with allies across the region.
"Politically, China aims to counter the military containment of democratic allies led by the United States," Su Tzu-yun, an analyst at Taiwan's Institute for National Defence and Security Research told AFP.
Following last August's visit to Taipei by Nancy Pelosi, then-speaker of the US House of Representatives, China staged its largest-ever war games around Taiwan.
Then in April this year, Beijing conducted a three-day "Joint Sword" military exercise to simulate the encirclement of the island, after Taiwan's President Tsai Ing-wen met US House Speaker Kevin McCarthy in California.
While Beijing has yet to issue any statements on its latest sorties, China's Global Times state tabloid posted a comment on the Weibo social media platform.
"The mainland and Taiwan belong to the same China, and Taiwan is a sacred and inalienable part of China," the post said, reiterating Beijing's long-standing policy.
"The People's Liberation Army's relevant combat training activities are necessary actions to safeguard national sovereignty and territorial integrity," it added, referring to China's military.
