The incursion came a day after NATO said China's increasingly aggressive military goals threatened international order -- and after G7 leaders issued a landmark statement urging peace in the Taiwan Strait.

Taiwan's defence ministry said it scrambled its own aircraft to broadcast warnings and deployed missile batteries to track the Chinese jets after they entered the island's southwest Air Defence Identification Zone (ADIZ).

The flights occurred the same day Beijing accused NATO of exaggerating the threat from China and "creating confrontation" after a vow from the Western allies to work together to counter the "systemic challenges" posed by its policies.

NATO leaders made the commitment on Monday, as US President Joe Biden renewed Washington's transatlantic ties at his first summit with the allies.

In a broad statement of intent, the leaders said China's increasingly assertive actions in building a nuclear arsenal and space and cyber warfare capabilities threatened the international order.

Democratic and self-ruled Taiwan lives under the constant threat of invasion by China, which has vowed to one day seize the island, by force if needed.

The two sides are separated by the narrow Taiwan Strait and some Chinese jets had crossed over the de facto border or so-called "median line" of the strait in previous incursions.

The sabre-rattling has increased dramatically since the 2016 election of President Tsai Ing-wen -- who rejects the idea the island is part of "one China".

Some analysts and US military officials have warned tensions between Taiwan and China are now at their highest since the mid-1990s.

The previous biggest incursion was in April when 25 Chinese jets breached the island's ADIZ after US Secretary of State Antony Blinken warned China not to attempt to change the status quo of Taiwan, saying to do so would be a "serious mistake".