A total of 29 Chinese warplanes entered Taiwan's self-declared air defence identification zone (ADIZ) on Tuesday, according to the island's Defence Ministry.
The Defence Ministry said the People's Liberation Army (PLA) Air Force planes were a mix of fighter jets, early warning and control aircraft, electronic warfare aircraft, anti-submarine aircraft, electronic intelligence aircraft, and aerial refuelling aircraft.
It was the third-highest daily number of Chinese jets entering Taiwan's ADIZ since the start of the year and comes less than a month after China sent 30 warplanes on a similar mission.
In response, the Taiwanese military scrambled combat aircraft to warn the Chinese jets away, issued radio warnings and deployed air defence missile systems to monitor the activities, the Defence Ministry added.
Taiwan and mainland China have been governed separately since the defeated Nationalists retreated to the island at the end of the Chinese civil war more than 70 years ago.
But China's ruling Chinese Communist Party (CCP) views the self-ruled island as part of its territory – despite having never controlled it.
Beijing has not ruled out military force to take Taiwan and has kept pressure on the democratic island over the past few years with frequent warplane flights into the island's ADIZ.
An ADIZ is unilaterally imposed and distinct from sovereign airspace, which is defined under international law as extending 12 nautical miles from a territory's shoreline.
The US Federal Aviation Administration defines it as "a designated area of airspace over land or water within which a country requires the immediate and positive identification, location and air traffic control of aircraft in the interest of the country's national security".
Tensions in the Taiwan Strait
The issue of Taiwan has been at the forefront of US-China relations in recent months.
Tensions between Washington, which is committed to supporting the island's self-defence, and Beijing over Taiwan dominated headlines earlier this month when their respective defence ministers met at the Shangri-La Dialogue defence conference in Singapore.
In a keynote speech in Singapore, Chinese Defence Minister Wei Fenghe accused the United States of being a "bully" in the region and vowed the PLA would "fight to the very end" to stop Taiwanese independence.
After the Shangri-La conference, China's Foreign Ministry reasserted previous statements that the Taiwan Strait "is not international waters".
"The waters of the Taiwan Strait extend from the coasts on both sides of the Strait to the centreline of the Strait, and are China's internal waters, territorial sea, contiguous zone and exclusive economic zone in that order," Foreign Ministry spokesman Wang Wenbin said in a briefing on June 13, citing the United Nations Convention on the Law of the Sea and China's domestic law.
Reiterating Beijing's stance on Wednesday, an editorial in China's state-run tabloid Global Times claimed that the entire Taiwan Strait – the 180km-wide body of water between Taiwan and mainland China – is not international waters, but rather completely under Beijing's jurisdiction.
The actions of US and foreign warships that regularly pass through the strait constitute provocations that violate Chinese sovereignty and are not innocent passage, a recognised international right, the Global Times said.
The US Navy sees things differently, regularly sending warships through the strait, including on May 10, when the guided-missile cruiser USS Port Royal made a transit.
Similarly to airspace, international law stipulates that a country's territorial waters extend 12 nautical miles from its coastline.