Former US President Donald Trump has called the federal indictment against him "ridiculous and baseless" in his first public appearance since the charges were announced.

A 37-count indictment made public on Friday accuses him of keeping sensitive documents at his Mar-a-Lago property.

The indictment amounted to "election interference" by the "corrupt" FBI and justice department, he said on Saturday.

He has denied any wrongdoing.

Mr Trump has been charged with mishandling hundreds of classified documents, including some about US nuclear secrets and military plans.

The indictment accused him of keeping the files at his Florida estate Mar-a-Lago in a ballroom and a shower.

He lied to investigators and tried to obstruct their investigation into his handling of the documents, the indictment alleged.

It is the first-ever criminal prosecution against a former US president.

In a speech on Saturday at a Republic Party convention in Georgia, Mr Trump said: "They're cheating, they're crooked, they're corrupt - these criminals cannot be rewarded, they must be defeated."

He joked that every time he flies over a "blue state" - one controlled by the Democrats - he gets subpoenaed.

Mr Trump, who is running for the White House again in 2024, called the indictment a "hoax" by the "corrupt political establishment", also describing it as a "joke" and a "travesty".

The speech went on for more than an hour.

It began with him thanking the "record crowd" as well as "patriots" from Georgia who had supported his White House bid - this was interspersed with an observation on the age of the building he was speaking in.

He then went onto criticise "sinister forces" that were running the country.

"We're going to stand up to the current political establishment … and we're going to finish the job we started, the most successful presidency," he said, a line that led to chants of "USA, USA" breaking out in the crowd.

"I will never yield, I will never be deterred," he said, before turning his attention to the groups he said were plotting against him.

This included Marxists, communists, "environmental extremists", Rinos - Republicans in Name Only - as well as "open border fanatics" and "radical left democrats".

Referencing the indictment, he claimed the highly-sensitive documents should have fallen under the Presidential Records Act, rather than the Espionage Act.

Under the Presidential Records Act, White House records are supposed to go to the National Archives once an administration ends. Regulations require such files to be stored securely.

He also said "gun-toting FBI agents" had raided Mar-a-Lago.

Special counsel Jack Smith, who oversaw the investigation, has denied the charges are politically-motivated, saying: "We have one set of laws in this country, and they apply to everyone."

As momentum starts to build towards the 2024 election, Mr Trump was speaking at a Republican Party convention in Columbus, Georgia, before moving onto another Republican Party event in Greensboro, North Carolina.

He is currently the frontrunner for the 2024 Republican nomination.

His former vice president Mike Pence - who this week was highly critical of his former boss when announcing his own run for the presidency - spoke earlier at the North Carolina event, although the pair are not expected to cross paths.

Georgia is likely to be a key battleground in the race for the White House, and is where Mr Trump narrowly lost to current President Joe Biden in 2020 - it could also be the scene of further legal jeopardy for the former president.

Officials in the state are currently looking into whether Mr Trump broke the law when he asked Georgia Secretary of State Brad Raffensperger to "find" the exact number of votes he needed to flip the vote in his favour. (BBC)

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