US President Joe Biden responded with frustration to an investigation's findings that he mishandled classified files and struggled to remember significant life events.

"I assure you, my memory is intact," he asserted during an unexpected press briefing.

In an emotional reaction to suggestions that he couldn't recall his son's death, he exclaimed, "How dare anyone question that?"

While the investigation concluded that Mr. Biden "knowingly retained and disclosed" classified documents, it opted not to pursue charges against him.

Special Counsel Robert Hur of the Department of Justice determined that Biden improperly retained classified materials related to military and foreign policy concerning Afghanistan post his tenure as vice president.

A critical 345-page report released earlier in the day highlighted limitations in the president's memory.

Despite Biden's efforts to address questions about his age and mental sharpness, he inadvertently referred to Egyptian leader Abdul Fattah al-Sisi as the "president of Mexico" during a discussion with reporters.

When asked about the latest developments in the Israel-Gaza conflict, he stated, "Initially, as you know, President Sisi of Mexico did not want to open up the gate to allow humanitarian aid to enter."

During the inquiry, Mr. Hur interviewed the 81-year-old president for over five hours, revealing Biden's difficulty recalling his time as vice president (2009-2017) and even the timeframe of his son Beau's death (2015).

During the Thursday night press conference, Biden, visibly moved, criticized portions of the report that questioned his recollection of events.

"Frankly, when I was asked the question, I thought to myself, was none of their d*mn business," he said.

"I don't need anyone to remind me when he [Beau Biden] passed away."

He said he was "very occupied... in the middle of handling an international crisis" when he was interviewed by the special counsel from 8-9 October last year - just as the Israel-Gaza war erupted.

The inquiry also said Mr Biden had shared some of the sensitive material from hand-written notebooks with a ghostwriter for his memoir, a finding that the president denied from the podium.

The special counsel concluded it would be difficult to convict the president of improper handling of files because "at trial, Mr. Biden would likely present himself to a jury, as he did during our interview of him, as a sympathetic, well-meaning, elderly man with a poor memory".

Opinion polls indicate the president's age is a concern for US voters ahead of November's White House election. But Mr Biden told reporters on Thursday he was the most qualified candidate.

"I am well-meaning," he said. "And am elderly. I know what the h3ll I'm doing. I put this country back on its feet.

"I don't need his recommendation."

Asked whether he took responsibility for having classified documents in his home, Mr Biden blamed his staff.

He said he didn't know they had put sensitive memos in his garage, where the special counsel says they were located next to a dog bed.

A BBC reporter at the White House's Diplomatic Reception Room described the atmosphere as tense.

When one journalist said the American people were concerned about his age, Mr. Biden said in reply: "That is your judgement, that is your judgement."

He insisted that his memory is "fine" and "has not gotten worse" during his presidency.

Mr Biden's legal team also criticised the special counsel's remarks about Mr Biden's apparent memory lapses.

"The report uses highly prejudicial language to describe a commonplace occurrence among witnesses: a lack of recall of years-old events," wrote White House lawyer Richard Sauber in a letter attached.

The top secret files were found at Mr Biden's house in Wilmington, Delaware, and his former private office from 2022-23.

The discovery came after a separate investigation charged former President Donald Trump, 77, with mishandling classified documents following his departure from the White House. He faces a trial in that case this May.

The Hur report distinguishes between both cases, saying Mr Biden handed over the documents to government archivists, while Mr Trump "allegedly did the opposite".

"According to the indictment, he not only refused to return the documents for many months, but he also obstructed justice by enlisting others to destroy evidence and then to lie about it," the report says about Mr Trump.

Mr Trump, in response, said the Justice Department prosecutor should cancel his classified files trial.

"If Special Counsel Jack Smith wants to do good for our Country, and help to unify it, he should drop all Litigation against Joe Biden's Political Opponent, ME, and let our Country HEAL," the Republican White House frontrunner posted on his platform, Truth Social.

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