A US F-18 Hornet fighter jet lands on US aircraft carrier USS George Washington during a military exercise off the west coast of South Korea, in this July 16, 2014 file photo. [Photo/Agencies]

The Chinese mainland lodged protest after two US fighter planes made a rare landing at an airport in southern Taiwan on Wednesday.

Two US navy F-18 fighters landed at Tainan Airport, which is for dual use by military and civilian aircraft, at 1:19 pm due to mechanical problems reported by one of them, Taiwan's military and aviation authorities confirmed.

The pilots landed after approval from the island's authorities.

"We have already lodged solemn representations with the US side," Foreign Ministry spokeswoman Hua Chunying said.

"We demand that the US strictly abide by the one-China policy and the Three Joint Communiques between China and the US and cautiously and appropriately handle relevant issues", she added.

The Taiwan authorities gave no explanation as to what mission the US fighters were on and why they were flying so close to the island.

The crew members and planes are safe, according to media reports.