Taiwan has reported a large incursion by Chinese warplanes for the second day running, a show of force that coincides with the first days of US President Joe Biden's term of office.

Sunday's operation involved 15 aircraft and followed a similar drill that led to a warning from Washington.

China sees democratic Taiwan as a breakaway province, but Taiwan sees itself as a sovereign state.

Analysts say China is testing the level of support of Mr Biden for Taiwan.

In the US's first public remarks on Taiwan since Mr Biden came into power, the US State Department reaffirmed its "rock-solid commitment" to helping it defend itself. There has been no official comment from the Chinese government.

China has carried out regular flights over the waters between the southern part of Taiwan and the Taiwanese-controlled Pratas Islands in the South China Sea in recent months.

But they are usually conducted by one to three reconnaissance or anti-submarine warfare aircraft, according to Taiwan.

Taiwan's defence ministry said eight Chinese bomber planes capable of carrying nuclear weapons, four fighter jets and one anti-submarine aircraft entered its south-western air defence identification zone on Saturday.

Sunday's operation involved 12 fighters, two anti-submarine aircraft and a reconnaissance plane, the ministry said. On both occasions, Taiwan's air force warned away the aircraft and deployed air defence missile systems to monitor the planes.