Republican front-runner Donald Trump has cancelled his rally in Chicago after protesters packed into the arena where it was to take place. There were isolated physical confrontations between some members of the crowd after the event was cancelled.

The announcement that the billionaire businessman would postpone the rally until another day led a large portion of the crowd inside the University of Illinois at Chicago Pavilion to break out into raucous cheers.

Meanwhile, supporters of the candidate started chanting 'We want Trump! We want Trump!'

There was no sign of Trump inside the arena on the college campus, where dozens of UIC faculty and staff had petitioned university administrators to cancel the rally. They cited concerns it would create a 'hostile and physically dangerous environment' for students.

Before the announcement the event wouldn't take place, a handful of intense verbal clashes took place between Trump supporters and protesters as the crowd waited for his arrival.

For the first time during his White House bid, the crowd appeared to be an equal mix of those eager to cheer on the real estate mogul and those overtly opposed to his candidacy.

When one African-American protester was escorted out before the event started, the crowd erupted into chants of 'Let them stay!'