Mr Trump declared he was the victim of "political persecution" and "prosecutorial misconduct", and heavily suggested it would spur him on to run again for the White House in 2024.
The raid marked a stunning and unexpected escalation of a Justice Department investigation into documents, including classified material, that Mr Trump may have taken with him to his Mar-a-Lago estate, in Florida, when he left office.
A lawyer for Mr Trump said the FBI agents took away about 12 boxes during a search on Monday morning that lasted hours, and was attended by Mr Trump's lawyer. Agents broke a padlock to the basement room where the boxes were stored.
These were separate to the 15 boxes Mr Trump returned to the National Archives in January.
Mr Trump said agents had broken into his safe, while members of his family claimed an office at Mar-a-Lago had been "ransacked".
The former president, who was in New York at the time of the raid, immediately released a campaign-style video, in which he called America a "nation in decline" but vowed: "Soon we will have greatness again."
In a statement on his Truth Social website on Tuesday night, Mr Trump claimed that "Biden knew all about this".
Among those urging Mr Trump to speed up his timeline for declaring his 2024 candidacy, Dan Scavino, his former social media manager Dan Scavino wrote on Twitter:
Mr Trump's team also sent out a fundraising request calling on "every single red-blooded American Patriot to step up" and donate to fight "this NEVERENDING WITCH HUNT".
One former Republican official said, if Mr Trump was not convicted of a crime following the high-profile raid, then "you've martyred him and guaranteed him the Republican nomination".
Ronna McDaniel, chairman of the Republican National Committee, accused the FBI of damaging US democracy.
She said: "President Trump is right when he compared this to Watergate. This is the government using an agency to spy on a potential opponent's campaign, and this is truly frightening. It is not what our democracy stands for. We have to take the reins of power back."
The unprecedented event looked set to fuel Republican fundraising and voter enthusiasm ahead of the mid-term elections in November, in which they are seeking to regain control of both chambers of Congress.
It also promised to intensify the already deep polarisation that has stagnated attempts at bipartisanship in Washington.
Kevin McCarthy, the Republican leader in the House of Representatives, said he would launch an oversight investigation into the Justice Department, which he accused of "intolerable politicisation".
He told Merrick Garland, the US attorney general, who almost certainly authorised the raid, to "preserve your documents and clear your calendar".
Even Mike Pence, Mr Trump's former vice-president who is now distanced from him, said: "No former president of the United States has ever been subject to a raid of their personal residence in American history."
Yesterday's action undermines public confidence in our system of justice and Attorney General Garland must give a full accounting to the American people as to why this action was taken and he must do so immediately.
— Mike Pence (@Mike_Pence) August 9, 2022
The FBI, which is part of the Justice Department and reports to Mr Garland, declined to provide a reason for the raid.
Stephen Miller, a former senior adviser to Mr Trump in the White House, claimed the FBI had been turned into a "Praetorian Guard" for the Biden administration.
He said: "This is an abomination. You have the sitting president Joe Biden, through his Justice Department, his FBI, conducting a raid on the person who is presumed to be his opponent in the next election."
Lara Trump, the former president's daughter-in-law, said: "There was no need to make such a big scene, to do something this insane, quite frankly, to a former president.
"They detest Donald Trump, not just on the Democrat side, but the general establishment, because he's not one of them, because he doesn't play their game. They are terrified he's going to announce any day that he's running for president in 2024."
She added: "I think it's only going to put more energy behind my father-in-law."
In stark contrast to the Republicans, leading Democrats reacted cautiously to the raid.
White House officials refuted accusations that they were politicising the Justice Department. They said Joe Biden knew nothing about the raid in advance, nor did anyone at the White House.
"The president was not briefed, was not aware of it," Karine Jean-Pierre, White House spokesman, told reporters. "No one at the White House was given a heads-up," she added.
And officials pointed out that Christopher Wray, director of the FBI, who also almost certainly approved it, was appointed by Mr Trump.
Nancy Pelosi, the Democratic speaker of the House of Representatives, said: "No person is above the law, not even a former president of the United States.
"To have a visit like that, you need a warrant. To have a warrant, you need justification. I do know that there has been chatter, more than chatter, about the presidential documents and how they must be preserved for history. Let's see what the justification was for the raid."
There was no indication of whether the FBI was looking for something specific.
However, David Axelrod, former chief strategist for Barack Obama, said: "I don't think this is a fishing expedition. I think they know what fish they were looking for.
"Merrick Garland is a notoriously cautious person. He would not have authorised it unless they believed they had significant evidence a crime had been committed."
One thing is very clear.
Garland would not have authorized this raid, and no federal judge would have signed off on it, if there weren't significant evidence to warrant it.
— David Axelrod (@davidaxelrod) August 8, 2022
Brian O’Hare, president of the FBI Agents Association, defended the raid, saying agents “perform their investigative duties with integrity and professionalism, and remain focused on complying with the law".
Others speculated that it had been carried out now so as not to avoid being too close to the midterms elections, which would risk influencing them.
Elie Honig, former prosecutor, said on Tuesday: "Today is just about 90 days out exactly from the mid-terms. That may be a reason why they did it today, because they want to stay clear of that if they're interpreting that as a 90-day rule."
Mick Mulvaney, Mr Trump’s former chief of staff, said the FBI raid was either the “most egregious political hit job” or part of the “most significant criminal investigation in our history”, depending on what was found.