"I'd like to punch him in the face," Trump said, remarking that a man disrupting his rally was escorted out with a smile on his face. "He's smiling, having a good time."
The GOP front-runner also ratcheted up his attacks on Sen. Ted Cruz, calling his Republican presidential rival "sick."
Trump claimed the protester was "nasty as hell" and accused the man of trying to punch the security officers forcing him out of the rally, though the man did not appear to be fighting off those officers.
"In the old days," Trump added, protesters would be "carried out on stretchers."
"We're not allowed to push back anymore," Trump said.
While Trump has at times urged his supporters not to hurt protesters, he has also repeatedly suggested that supporters should be handled more roughly.
When a Black Lives Matter protester was punched and kicked
by attendees at a Trump rally last fall, Trump remarked the next day that "maybe he should have been roughed up."
Shortly after that incident, the Trump campaign began making an announcement at the start of its rallies urging supporters to not harm any protesters, but instead shout "Trump, Trump, Trump" and wait for security officials to escort the protesters out.
The Trump campaign did not make the announcement before Monday's rally. It was unclear what the man who disrupted it was protesting.
Moments earlier, another man raised a banner that read, "Veterans to Trump: End hate speech against Muslims."
Trump on Cruz: 'Something wrong with this guy'
Of Cruz, Trump took aim at the senator's campaign tactics, including the attack ads Cruz and his allies have run against Trump.
"This guy is sick. There's something wrong with this guy," Trump said.
Cruz's campaign has run several ads scrutinizing Trump's record on a variety of issues important to conservatives, including Trump's past support for abortion rights and stricter gun control measures.
"I missed the part where Donald challenges our facts?" Cruz spokeswoman Catherine Frazier told CNN. "He can't, because our ads are true -- he is not a real conservative. He can't defend his record, so like a frustrated child, he resorts to name calling."
Trump has repeatedly slammed Cruz since the Texas senator surged in the polls ahead of the Iowa caucuses and has since ramped up his attacks on him since Cruz beat Trump in the Iowa contest.
The Texas senator, meanwhile, has criticized Trump over a range of issues, from Trump's support for abortion rights in 1999 to Trump's use of eminent domain laws for personal gain. He's also suggested that Trump, who has vowed to repeal Obamacare, supports the signature health care law, pointing to Trump's September interview with "60 Minutes" in which Trump said that "everyone's got to be covered" when asked if he supported universal health care.
Trump: 'What the hell is a caucus?'
Trump's Monday rally came on the eve of the Nevada caucuses and Trump spent much of his speech urging his supporters to head to the caucuses to give him what would be his third consecutive victory in the GOP primary.
"They're all saying Trump's gonna win tomorrow. Just assume we're going to tie," Trump told his supporters on Monday night.
And Trump, who has slammed the caucus process since losing to Cruz in Iowa, told his supporters to forget about the slightly more arduous caucus process, which involves voters meeting at a caucus location and hearing pitches for each candidate before casting their vote.
"Forget the word caucus, just go out and vote, OK?" Trump said. "What the hell is a caucus? Nobody even knows what it means."
Cruz supporter Beck denounces Trump as a 'bully'
At a Cruz rally in Elko earlier on Monday, supporter Glenn Beck condemned those sorts of outbursts by Trump -- calling him a bully and asking rural Nevada voters to reject that kind of rhetoric.
Beck faulted Trump for threatening protesters at earlier rallies, and noted that Trump issued a threatening tweet on Monday to the Ricketts family, which has been politically active in recent cycles.
"I hear the (Ricketts) family, who own the Chicago Cubs, are secretly spending $'s against me. They better be careful. They have a lot to hide," Trump tweeted.
"When we have a candidate that threatens people," Beck said. "This is not American. This is not equal justice. This is not who were are."
"If we give in to our anger, if we start to go down that path and we start to listen to the bullies. We lose what made us great," Beck said before introducing Cruz.