Former US President Donald Trump denounced a "political persecution" after pleading not guilty to dozens of criminal counts.

In a historic first court appearance as a federal defendant, Trump is accused of mishandling some of the US government's most sensitive secrets and scheming to prevent their return.

Speaking to supporters after the hearing in Florida, the former US president denounced the charges as "political persecution".

"More importantly, it's a political persecution like something straight out of a fascist or communist nation. As president, the law that applies to this case is not the Espionage Act, but very simply the Presidential Records Act which is not even mentioned in this ridiculous 44-page indictment. Under the Presidential Records Act, which is civil, not criminal, I have every right to have these documents", said Donald Trump.

Donald Trump is the favourite candidate to fight next year's presidential election for the Republicans.

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.