Former US President Donald Trump appeared at a courthouse in Miami, Florida, on Tuesday and pleaded not guilty to concealing classified government documents. He has become the first person to serve as US president to be charged with a federal crime.

Trump faces 37 criminal counts, including concealing files on national defense, the military capabilities of other countries and nuclear secrets. Last August, FBI agents seized hundreds of documents from his estate in Florida.

After his arraignment, Trump went straight from the courthouse to a restaurant to meet with his supporters. He said the indictment is a "rigged deal" and a "political hit job" and that the US is a "corrupt" country.

He alleges that President Joe Biden orchestrated the charges to undermine his presidential campaign. Many lawmakers in the Republican Party have called it a "witch hunt."

This is the second time this year Trump has had to surrender to authorities. In April, he pleaded not guilty in New York to state charges related to hush money paid to an adult movie star.