Donald Trump said on Thursday he has been indicted over his handling of classified documents after leaving office, the US ex-president’s most serious legal threat yet as a firestorm of criminal investigations imperils his bid for a second White House term.

“The corrupt Biden administration has informed my attorneys that I have been indicted, seemingly over the boxes hoax,” Trump wrote on his Truth Social platform as he broke the bombshell news of a historic moment for the United States: the first time a sitting or former commander-in-chief has ever faced federal charges.

There was no immediate confirmation from the Justice Department regarding Trump’s assertion.

A Trump attorney, Jim Trusty, told CNN his client has been indicted on seven charges including the willful retention of documents in violation of the Espionage Act, making false statements, obstruction of justice and a count of conspiracy.

Though the precise details of the charges were not immediately clear, people familiar with the matter told The New York Times that the conspiracy charge was related to obstruction of justice.

In his post, Trump, who is running for president again, said he has been summoned to a federal courthouse in Miami next Tuesday — the day before his 77th birthday.

“I never thought it possible that such a thing could happen to a former president of the United States,” he wrote.

His announcement came a day after US media said federal prosecutors had informed the former president’s lawyers that he is the target of the probe into his handling of classified documents.

He was already the first former or sitting president to be charged with a crime — in his case over election-eve hush money payments to a porn star who said she had an affair with him. That indictment was handed down by Manhattan’s district attorney in March.

In a statement after his initial online posts, the Trump campaign lashed out at what it called an “unprecedented abuse of power,” and called for the indictment to be thrown out.

Dark day

In a defiant video released after he shared the news, Trump repeatedly declared his innocence and framed the indictment as a form of election interference by a Justice Department “weaponised” by Joe Biden’s administration.

“They come after me because now we’re leading in the polls again by a lot against Biden,” Trump says in the clip. “Our country is going to hell and they come after Donald Trump […] We can’t let this continue.”

His allies in Congress swiftly stood by him, like House Judiciary Committee chairman Jim Jordan.

Top Republican leadership, including Speaker of the House of Representatives Kevin McCarthy who has had a rollercoaster relationship with the former president, also rushed to defend Trump.

“Today is indeed a dark day for the United States of America. It is unconscionable for a President to indict the leading candidate opposing him,” House Speaker Kevin McCarthy said in a statement.

“I, and every American who believes in the rule of law, stand with President Trump.”

Special counsel Jack Smith, named by US Attorney General Merrick Garland, has been looking into a cache of classified documents that Trump had stored at his Mar-a-Lago residence in Florida after leaving the White House.

The FBI carted away some 11,000 papers after serving a search warrant on Mar-a-Lago in August, and obstruction-of-justice charges could be a result of his resisting efforts to recover the trove.

Trump eventually turned over 15 boxes containing almost 200 classified documents to the National Archives in January 2022 but was subpoenaed for any outstanding records in his possession.

When asked about the charges on Thursday night, Smith’s spokesman Peter Carr told AFP, “We are declining to comment.”

Mounting legal woes

Some Democratic lawmakers spoke out following Thursday’s extraordinary revelation.

Trump’s indictment “is another affirmation of the rule of law,” House Democrat Adam Schiff said.

“For four years, he acted like he was above the law,” Schiff added. “But he should be treated like any other lawbreaker. And today, he has been.”

Trump has repeatedly denied wrongdoing in the documents’ case, telling a Fox News town hall event on June 1 that “everything I did was right.”

But he has openly acknowledged taking and storing the documents, undermining his lawyers’ suggestion he took the stash inadvertently in the confusion of a chaotic departure.

“This evidence just adds to the mound of stuff that already exists, and no one piece is the ‘be all and end all,’ but when you put them all together, the case is so strong,” former Watergate prosecutor Jill Wine-Banks told MSNBC.

“You cannot imagine his getting away with this.”

The latest indictment comes with Trump facing numerous other probes as he bids to be the Republican nominee to challenge US President Joe Biden for the presidency in 2024.

Smith is also looking at whether Trump should face charges over the 2021 US Capitol riot, and Georgia prosecutors are investigating whether Trump illegally attempted to overturn the 2020 presidential election outcome there.

The former president has already been charged with dozens of financial crimes as part of an alleged hush-money scheme to silence a porn star claiming she had sex with him and is due to go on trial next March, in the middle of primary election season.