Donald Trump was rushed off the stage by Secret Service agents at a Nevada rally after a man close to the podium shouted: “Gun!”
The Republican US presidential nominee was speaking to supporters at the rally in Reno when a disturbance broke out in the crowd near the stage. Two agents quickly surrounded Mr Trump and hustled him away.
In a statement, the Secret Service said a person in front of the stage had shouted “Gun!” but no weapon was found after a search. The person was apprehended and an investigation was taking place, it added.
Upon his return to the stage a few minutes later, billionaire Mr Trump thanked the Secret Service and told the crowd: “Nobody said it was going to be easy for us. But we will never be stopped. Never ever be stopped.”
The Secret Service statement noted that magnetometer screening was used at presidential campaign sites.
“All general public attending these events must go through a magnetometer screening prior to entering a protected area,” the agency said.
Fighting as a party of one, Mr Trump vowed to press into Democratic strongholds over the campaign’s final days as Hillary Clinton looked to A-list celebrities and politicos to defend her narrowing path to the presidency.
The divisive Republican outsider conceded he was largely on his own - even as he promised to march into Minnesota, a state that has not backed a Grand Old Party (GOP) presidential nominee in more than 40 years.
“Hillary Clinton has all of these celebrities and failed politicians out campaigning for her,” a defiant Mr Trump declared in North Carolina, one of four battleground states he was visiting on Saturday. “I just have me, but I have my family.”
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Responding to Mr Trump’s push, Democrat Mrs Clinton announced plans to devote valuable attention to Michigan, another unlikely battleground where both she and President Barack Obama planned to campaign on Monday.
The Democratic nominee faced dark skies in Florida, fighting intense rain and wind in a key battleground state before a Pennsylvania appearance with pop singer Katy Perry. Mrs Clinton will campaign on Sunday with basketball superstar Lebron James, having shared the stage the night before with music diva Beyonce and her hip hop mogul husband Jay Z.
“Tonight, I want to hear you roar,” a smiling Mrs Clinton said before introducing Perry for a Saturday night performance in Philadelphia.
Perry, who hugged Mrs Clinton while wearing a purple cape bearing the words “I’m with Madam President”, shouted: “In three days, let’s make history!”
The final-days scramble highlighted sharp differences between the campaigns in a turbulent 2016 campaign season.
Backed by Mr Obama and her party’s political elite, Mrs Clinton spent much of the last year fighting to unify Mr Obama’s coalition of minorities and younger voters, aided at times by Mr Trump’s deep unpopularity among women in both parties.
Mr Trump has courted working-class white voters on the strength of his own celebrity, having scared off many would-be Republican allies during a campaign marred by extraordinary gaffes and self-created crises.
Just four weeks ago, a video emerged in which a married Mr Trump admitted to kissing women and grabbing their genitalia without their permission.
House of Representatives speaker Paul Ryan campaigned on Saturday alongside Mr Trump’s running mate Mike Pence in a rare show of unity - but not with Mr Trump himself.
He encouraged Republicans to “come home” to support Mr Trump in Mr Ryan’s home-state Wisconsin, ignoring for a day his icy relationship with the Republican nominee.
Even with the damaging Trump video, Mrs Clinton has faced extraordinary challenges of her own in recent days after the FBI confirmed plans to renew its focus on the former secretary of state’s email practices.
The development is seen as particularly threatening for her in states like Michigan, Pennsylvania and New Hampshire that do not offer early voting.
At least 41 million Americans across 48 states have already cast ballots, according to an Associated Press analysis - significantly more votes four days before election day on Tuesday than voted early in the 2012.