Donald Trump recorded saying he kept classified file after leaving office

US prosecutors have obtained an audio recording of Donald Trump in which he acknowledges keeping a classified document after leaving the White House.

CNN first reported that investigators had the tape, and people familiar with the matter later told the BBC's US partner CBS this was the case.

The justice department is investigating Mr Trump's handling of classified material. He denies wrongdoing.

The inquiry is reported to be nearing its end and could result in charges.

The audio recording is said to be from a meeting at Mr Trump's New Jersey golf club in July 2021, which is around six months after he left office.

Two people familiar with the matter told CBS that Mr Trump can be heard acknowledging there are national security restrictions on a military memo because it details a potential attack on Iran.

He says it is still classified and should have been declassified before leaving the White House, one person said.

Mr Trump also says he wants to share information from the document but knows his ability to declassify it is limited because he is no longer president, CNN reported.

It is not clear whether Mr Trump had the document during the meeting or was just describing it to several aides who were there. Other reports suggest the sound of rustling paper can be heard.

The tape appears to contradict Mr Trump's repeated argument that he declassified all material he removed from the White House. It could also prove to be a key piece of evidence if prosecutors seek to show the former president was aware he should not be in possession of classified documents.

Neither the BBC or CBS News have listened to the audio and it has not been made public.

It has been handed over to justice department investigators who are being overseen by special prosecutor Jack Smith.

Their investigation, which has ramped up in recent weeks, is examining the removal of hundreds of classified government documents from the White House which were then taken to Mr Trump's Florida estate, Mar-a-Lago, after he left office.

Investigators are assessing how these documents were stored and who may have had access to them. They are also examining how his team responded to a request for security footage from his Florida estate.

Mr Smith will ultimately decide whether the former president should face criminal charges. Among other statutes, the justice department believes Mr Trump may have violated the Espionage Act by keeping national security information after he left office.

Mr Trump, who is running for president again in 2024, faces several other legal investigations. He was recently indicted in New York over hush money payments made to a porn star. He has pleaded not guilty.

He is also the subject of an investigation in Georgia over his alleged efforts to try and overturn the 2020 presidential election results in the state.