Hong Kong(CNN) China has sent a record 18 nuclear-capable H-6 bomber aircraft into Taiwan's air defense zone, the island's Defense Ministry said Tuesday, as Beijing continues to step-up pressure on the self-ruled island.
The 18 bombers were part of 21 total Chinese warplanes sent into Taiwan's southwest air defense identification zone -- a buffer of airspace commonly referred to as an ADIZ -- in the 24-hour span between Monday morning and Tuesday morning, according to Taiwan's Defense Ministry.
The ministry said it monitored the situation and employed its fighter jets as well as land-based missile systems to track the Chinese planes.
The flights represent the largest number of H-6 sorties in a 24-hour period since Taipei began releasing daily data on Chinese fighter incursions in 2020.
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.
China's ruling Chinese Communist Party views Taiwan -- a democratically governed island of 24 million -- as part of its territory, despite having never controlled it. It has long vowed to "reunify" the island with the Chinese mainland, by force if necessary.
Tensions surrounding Taiwan have increased markedly this year. A visit to the island by United States House Speaker Nancy Pelosi in August prompted Chinese fury and an immediate flurry of military exercises.
Since then, Beijing has stepped up military pressure tactics on the island, sending fighter jets across the median line of the Taiwan Strait, the body of water separating Taiwan and China.
For decades, the median line had served as an informal demarcation line between the two, with military incursions across it being rare.
In November, US President Joe Biden met Chinese leader Xi Jinping in-person for the first time during his presidency at the G20 summit in Indonesia. Afterward, Biden described the three-hour meeting as "open and candid," and cast doubt on an imminent invasion of Taiwan.
Formal bilateral talks on climate cooperation are expected to resume as well as part of a broader set of agreements between Biden and Xi -- with China having previously halted talks as part of retaliation for Pelosi's visit to Taiwan.