TAIPEI (AFP) - More than 20 Chinese military planes flew into Taiwan's air defence zone on Tuesday (Aug 2), officials in Taipei said, as US House Speaker Nancy Pelosi began her controversial visit to the self-ruled island that Beijing considers its territory.

The island's defence ministry said in a statement on Twitter: "21 PLA aircraft... entered #Taiwan's southwest ADIZ on August 2, 2022," referring to the air defence identification zone.

The ADIZ is not the same as Taiwan's territorial airspace but includes a far greater area that overlaps with part of China's own air defence identification zone and even includes some of the mainland.

Several US warships, meanwhile, were reported to be cruising in waters near Taiwan, according to US officials.

The US Navy’s Seventh Fleet said the nuclear-powered aircraft carrier Ronald Reagan, which is usually based near Japan, was operating in the Philippine Sea, south of Taiwan.

The Ronald Reagan was accompanied by the USS Higgins, a destroyer that is part of its strike group, a US Navy official said, on condition of anonymity.

The aircraft carrier and its group are “on a routine operation in the Western Pacific,” a US official said, on condition of anonymity.

Additionally, the amphibious assault ship USS Tripoli was operating east of Taiwan, the US Navy official said, confirming reports from the United States Naval Institute (USNI), a professional association with close ties to the Navy.

The Ronald Reagan and the Tripoli are both carriers of the latest generation F-35 fighter jets, according to the USNI.

US officials have sought to reassure Beijing that the positioning of these two ships in the region was not linked to the visit by Pelosi, the highest-ranking elected US official to visit the island since predecessor Newt Gingrich travelled there in 1997.

National Security Council spokesman John Kirby told CNN that Washington would make sure Pelosi had a “safe and secure visit.”