Republican presidential candidate Donald Trump has cancelled one of his signature rallies over safety concerns after protesters swarmed into the arena where he was due to speak.

The announcement that the brash billionaire businessman would postpone the rally led a large portion of the crowd inside the University of Illinois at Chicago Pavilion to break out into raucous cheers. Many rushed on to the floor, jumping up and down with their arms up in the air.

"Trump represents everything America is not and everything Chicago is not," said student Kamran Siddiqui, 20. "We came in here and we wanted to shut this down. Because this is a great city and we don't want to let that person in here."

Some supporters of the Republican front-runner started chanting "We want Trump!" in response to the celebrations and there were some isolated physical confrontations between people in the crowd. Chicago police said five people were arrested.

"It's a shame," said Trump supporter Bill Tail, 43. "They scream about tolerance but are being intolerant themselves. That doesn't make sense."

As Mr Trump attempts to unify a fractured Republican Party ahead of next week's slate of winner-take-all primary elections, the confrontations between his legion of loyal supporters and protesters who accuse him of stoking racial hatred have become increasingly contentious, underscoring concerns about the divisive nature of his candidacy.

A North Carolina man was arrested after video footage showed him punching an African-American protester being led out of a Trump rally in the state on Wednesday. At that event, Mr Trump recalled a past protester as "a real bad dude".

"He was a rough guy, and he was punching. And we had some people - some rough guys like we have right in here - and they started punching back," he said. "It was a beautiful thing."

At Mr Trump's earlier rally in St Louis, he was repeatedly interrupted by protesters. Police there charged nearly three dozen people with general peace disturbance and one person with assault.

Texas senator Ted Cruz, Mr Trump's closest rival in the Republican race, said the billionaire had created "an environment that encourages this sort of nasty discourse".

Speaking at a suburban Chicago party dinner about 30 miles away from the university campus, he called the incident a "sad day".

"Political discourse should occur in this country without the threat of violence, without anger and rage and hatred directed at each other," he said.

Mr Cruz said blame for the events in Chicago rested with the protesters, but added: "In any campaign responsibility starts at the top.

"When the candidate urges supporters to engage in physical violence, to punch people in the face, the predictable consequence of that is that is escalates.

"Today is unlikely to be the last such incidence."

After postponing the Chicago rally Mr Trump said he did not "want to see people hurt or worse", telling MSNBC: "I think we did the right thing."

But Chicago police said they had sufficient manpower on scene to handle the situation and did not recommend that Mr Trump cancel the rally. That decision was made "independently" by the campaign, said police spokesman Anthony Guglielmi.

Mr Trump said the anger on display in Chicago was not directed at him or his campaign, but rather a manifestation of the public's deep frustration with economic conditions in the US.

"Our businesses are being taken away from us, our businesses are being moved out of the country," he said on Fox News. "This is a demonstration against economic conditions on both sides."

But many of the protesters in Chicago said they were there to specifically to stop Mr Trump from speaking.

"Our country is not going to make it being divided by the views of Donald Trump," said Jermaine Hodge, a 37-year-old Chicago resident who owns a haulage company. "Our country is divided enough. Donald Trump, he's preaching hate. He's preaching division."

Dozens of University of Illinois at Chicago faculty and staff had petitioned administrators earlier in the week to cancel the Friday night rally, citing concerns it would create a "hostile and physically dangerous environment" for students.

One Trump supporter at the Chicago rally said Mr Trump had created the environment that led to Friday night's melee by holding the event at the school - a civil and immigrant rights organising hub with large minority student populations.

"I think he was kind of provoking things, to be honest with you," said Dan Kozak, 23, from suburban Tinley Park. "He could have picked the suburbs and nothing would have happened."

Hours before the Chicago event was due to start, hundreds of people lined up to get into the arena. Trump backers were separated from an equally large crowd of anti-Trump protesters by a heavy police presence and barricades.

Once inside, some supporters and protesters engaged in a series of intense verbal altercations. For the first time during his White House bid, the crowd at one of his events appeared to be an equal mix of those eager to cheer on the real estate mogul and those overtly opposed to his candidacy.