Former US president Donald Trump said on Monday that his residence at the Mar-a-Lago club in Florida was being raided by a “large group” of FBI agents.

In a statement posted on Twitter by an affiliated account, Trump said his Florida residence “is currently under siege, raided and occupied by a large group of FBI agents. Nothing like this has ever happened to a President of the United States before.”

He added that the “unannounced raid was not necessary or appropriate” since he had been “working and co-operating” with the relevant government authorities, although he did not specify on what topic. “They even broke into my safe!” Trump wrote.

The Department of Justice declined to comment. If confirmed, the search by the FBI would represent a remarkable step by US authorities to scrutinise the actions of a former president.

US media widely reported that the move related to the previous discovery of 15 boxes of classified documents from his time at the White House — including some that were marked “top secret” — that had been found at his Florida home.

Searching the home of a former US president would have to be authorised by a judge and most likely approved at the highest levels of the justice department, including attorney-general Merrick Garland.

In February, Garland had told reporters that the justice department was notified by the National Archives about the classified material at Mar-a- Lago, adding: “We will do what we always do under these circumstances: look at the facts and the law and take it from there.”

Trump’s announcement of the FBI action comes after he has faced growing pressure over his efforts to overturn the results of the 2020 presidential election, which he lost to Joe Biden, and the January 6 attack on the US Capitol just a few days before the transfer of power.

It also comes as Trump weighs a bid for a second term as president in 2024. He still maintains a solid grip on the conservative base of the Republican party, making him the natural favourite in a primary for his party’s nomination.

But some Republicans have been searching for alternative candidates, such as Florida governor Ron DeSantis or former vice-president Mike Pence, on the grounds that Trump could be a toxic choice in a general election given the chaos of his four years in office and his denial of the 2020 vote result.

The White House did not respond to a request for comment on Trump’s announcement of a raid.