A man suspected of hiding for nearly 12 hours in an apparent attempt to assassinate Donald Trump at his Florida golf course has been charged with two gun-related crimes, a day after authorities say he was spotted in the bushes with a rifle as the former US president played nearby.

Trump, the Republican presidential candidate in the November 5 election, was unharmed. But the incident raised fresh questions about how an armed suspect was able to get so close to him, just two months after another gunman fired at Trump during a July 13 rally in Butler, Pennsylvania, grazing his ear with a bullet.

Trump's visit to his golf course in West Palm Beach was not on his public schedule, Acting US Secret Service Director Ronald Rowe told reporters, and it was not clear whether the suspect knew Trump would be there.

The Secret Service opened fire after an agent sweeping the course saw a rifle barrel poking out of the bushes a few hundred yards away from the former president, who was on the fairway of the fifth hole.

"All of a sudden we heard shots being fired in the air. I guess probably four or five," Trump said during an event on X Spaces.

"Secret Service knew immediately it was bullets, and they grabbed me... We got into the carts and we moved along pretty, pretty good. I was with an agent, and the agent did a fantastic job."

While praising the Secret Service agents, he added: "We do need more people on my detail."

The gunman fled in a sports utility vehicle, according to the complaint. Officers found a loaded assault-style rifle with a scope, a digital camera and a plastic bag of food left behind.

A suspect, identified as Ryan Routh, 58, was arrested about 40 minutes later driving north on Interstate 95. When asked if he knew why he had been stopped, Routh "responded in the affirmative", according to the complaint. The license plate on his vehicle had been reported stolen from another car.

Records show a phone associated with Routh was located at the golf course starting at 1.59am on Sunday morning, 11.5 hours before the incident.

The suspect was on the "public side" of a fence along the golf course's boundary, Rowe said at a news conference. He did not have a line of sight to Trump and did not fire any shots, Rowe said.

Routh was the subject of a 2019 tip to the FBI alleging that he was a convicted felon who illegally possessed a firearm, said Jeffrey Veltri, the agent in charge of the FBI's Miami field office.

The complainant was unable to verify the information when the FBI investigated the tip, Veltri said.

Police bodycam footage shows the arrest of suspected gunman. – AP

Routh made a brief appearance in federal court in West Palm Beach, where he was charged with possession of a firearm as a convicted felon and possession of a firearm with an obliterated serial number. More charges are likely to follow.

The defendant invoked his right to an attorney when investigators sought to question him, Rowe said.

Routh has at least two prior felony convictions, both in North Carolina, according to the criminal complaint.

In 2002, Routh pleaded guilty to possession of an unregistered fully automatic gun, defined in North Carolina law as a weapon of mass destruction, according to the county district attorney's office, and was sentenced to probation. He was also convicted of possessing stolen goods in 2010.

Suspect wrote a book urging Iran to assassinate former president Donald Trump. – AP

Trump's campaign schedule will remain unchanged, according to a source with knowledge of the matter. He is scheduled to unveil a new cryptocurrency business on X on Monday night, and will host a town hall in Michigan on Tuesday and a rally in Wednesday in New York.

Trump blamed President Joe Biden and Vice President Kamala Harris, the Democratic presidential candidate, for the apparent assassination attempt. He claimed the suspected gunman was acting on Democrats' "highly inflammatory language", though authorities have not yet offered evidence of any motive.

"Their rhetoric is causing me to be shot at, when I am the one who is going to save the country, and they are the ones that are destroying the country – both from the inside and out," he said, according to Fox.

Harris said on X: "Violence has no place in America."

Speaking at a Philadelphia event, Biden said, "In America, we resolve our differences peacefully at the ballot box, not at the end of a gun."

Biden commends Secret Service, declares there is 'no place for political violence’. – AP

Secret Service under pressure

The Secret Service, which protects US presidents, presidential candidates and other high-level dignitaries, has been under intense scrutiny since the earlier attempt on Trump's life.

That led to the resignation of Director Kimberly Cheatle. The service bolstered Trump's security detail following the July 13 attack, in which the gunman was shot dead by responding agents.

The agency "needs more help," including possibly more personnel, Biden told reporters, adding: "Thank God the president's OK."

House of Representatives Speaker Mike Johnson, who convened a bipartisan task force to investigate the first assassination attempt, told Fox News that Congress would also examine the latest incident.

"We need accountability," said Johnson, who called for more resources to protect Trump.

Rowe, who took over the Secret Service after Cheatle's resignation in July, told Congress on July 30 he was "ashamed" of security lapses in the earlier attack.

Suspect is Ukraine sympathiser

Routh is a staunch supporter of Ukraine and traveled there after Russia's 2022 invasion, seeking to recruit foreign fighters. Ukrainian officials distanced themselves from Routh, and The International Legion, where many foreign fighters in Ukraine serve, said it had no links with Routh.

Profiles on X, Facebook and LinkedIn with Routh's name contained messages of support for Ukraine as well as statements describing Trump as a threat to US democracy.

Reuters was not able to confirm that the accounts belonged to the suspect. Public access to the Facebook and X profiles was removed hours after the incident.

Secret Service acting director says agency’s protective measures are 'working'. – AP

Authorities are examining Routh's online presence, including social media, Rowe said.

Harris and other Democrats have cast Trump as a danger to US democracy, citing his effort to overturn his defeat in the 2020 election, which led to the January 6, 2021, assault on the US Capitol. Harris has promised unwavering support for Ukraine if elected.

Trump has expressed skepticism about the amount of aid the US has provided Ukraine and has vowed to end the war immediately if elected. He told Reuters last year that Ukraine might have to cede some territory to gain peace.

Ryan Routh appears in federal court in West Palm Beach, Florida. – Reuters