US President Joe Biden has been interviewed as part of a probe into his handling of classified documents after he left the vice-presidency in 2017.

Mr. Biden met voluntarily with Special Counsel Robert Hur at the White House over two days, officials said.

Mr. Hur was appointed after a separate investigation was launched into secret documents found at Donald Trump's home.

Mr. Biden has not been charged with any crime. It is not unusual for presidents to be interviewed by investigators.

Ian Sams, a spokesman for Mr. Biden, said in a statement that the interview was conducted over the course of Sunday and Monday.

It was personally carried out by Mr. Hur, who was chosen by US Attorney General Merrick Garland to lead the investigation. He added that the interview had “concluded” by the end of Monday.

“As we have said from the beginning, the President and the White House are cooperating with this investigation, and as it has been appropriate, we have provided relevant updates publicly, being as transparent as we can consistent with protecting and preserving the integrity of the investigation,” Mr Sams told reporters.

“We would refer other questions to the Justice Department at this time.”

The documents were discovered by aides to Mr Biden in an office he used after departing the vice-presidency, and before he launched his bid for the White House. (BBC)