(AFP) - Donald Trump pleaded not guilty Tuesday to dozens of criminal counts of mishandling some of the US government's most sensitive secrets and scheming to prevent their return, in a historic first court appearance as a federal defendant.

The former president -- and the favorite to fight next year's election for the Republicans -- gave himself up to US Marshals in Miami for a hearing that set up the unprecedented scenario of a White House race litigated from the courtroom as well as at the ballot box.

On the eve of his 77th birthday, Trump appeared before a magistrate judge to be formally presented with 37 counts under seven charges brought by a special counsel probe that opened after an FBI raid of his Florida mansion 10 months ago.

But he dismissed his prosecution as politically-motivated in a speech to supporters framing the indictment as an effort to interfere in the 2024 election.

"Today we witnessed the most evil and heinous abuse of power in the history of our country. Very sad thing to watch," Trump said after returning to his summer residence in New Jersey.

The hearing -- just weeks after Trump denied state level financial fraud charges in a separate case in Manhattan -- came with the former reality TV star's mounting legal woes threatening to derail his bid to return to the Oval Office.

The US government -- which has never before prosecuted a former president -- accuses Trump of violating the Espionage Act and other laws when he removed classified documents upon leaving office in 2021 and failed to give them up to the National Archives.

Authorities say he conspired to thwart investigators and knowingly shared national security secrets with people who did not have the requisite clearance.

After the hearing Trump jetted from Miami back to his golf club in Bedminster, New Jersey, where he blamed President Joe Biden for his prosecution.

"A corrupt sitting president had his top political opponent arrested on fake and fabricated charges -- of which he and numerous other presidents would be guilty -- right in the middle of a presidential election, in which he's losing very badly," said Trump, speaking from the front of the clubhouse, at a podium flanked by American flags.

He was cheered by several hundred supporters, including 100 members of a conservative organization of Vietnamese Americans who had donned matching red dresses and chanted: "We love Trump."

- 'Travesty' -

Trump enjoys strong backing from Republican voters, 81 percent of whom believe the charges against him are politically-driven, according to a new Ipsos poll.

Antonio Rufa, 30, who had come to Bedminister to support the tycoon, called Trump's indictment "a travesty" while 57-year-old Vincent Larusso said the prosecution was designed to prevent Trump from running for reelection.

"This is not democracy and people can see this from a hundred miles away," Larusso told AFP.

The government has recovered more than 300 documents with classified markings from Trump since officials discovered his correspondence with North Korean leader Kim Jong Un was missing, US media reported.

The records were the work of top national security and law enforcement agencies such as the CIA and NSA, according to prosecutors, and some concerned the military and nuclear capabilities of the United States and foreign countries, and "plans for possible retaliation in response to a foreign attack."

The 49-page indictment, dismissed by Trump as "ridiculous," includes photographs of boxes of records stacked at Mar-a-Lago, his Palm Beach residence, in a ballroom and in a bathroom and shower.

One image showed that by December 2021, some of the boxes that had been moved to a storage room fell, with their contents spilling across the floor.

- 'Don't play ball' -

Trump dismissed his attorneys' attempts to comply with a subpoena for the return of the records, according to the indictment, which quoted him asking a lawyer: "What happens if we just don't respond at all or don't play ball with them?"

The runaway frontrunner in the 2024 Republican primary -- Trump leads second-placed Ron DeSantis by more than 30 points -- has been impeached twice over allegations of misconduct in office and was recently found liable for sexual abuse.

He faces indictment or ongoing scrutiny in four criminal probes -- in Washington, Florida, Georgia and New York -- and could find himself on trial in multiple cases as he campaigns to return to the White House.

The pugnacious billionaire has repeatedly complained that the investigations against him amount to a baseless "witch hunt" -- and has vowed to stay in the race regardless of the outcome of the documents case.

He said Monday he would appoint a special prosecutor on his return to office to investigate Biden, who is not facing any credible accusations of criminality.

Republican leaders in Congress and Trump's rivals for the party's presidential nomination have largely glossed over the gravity of the allegations against him, instead attacking the Justice Department.

Fewer than one percent of US federal defendants go to trial and win acquittal, according to the Pew Research Center. The vast majority -- around 90 percent -- plead guilty.

© Agence France-Presse