Donald Trump is under fire from rivals who blamed his incendiary rhetoric for a violent outbreak Friday between protesters and supporters at the Republican frontrunner's rally in Chicago. Trump cancelled the event after demonstrators scuffled with his supporters and police struggled to maintain order, with hundreds of protesters showing up. "When you have a campaign that affirmatively encourages violence, when you have a campaign that is facing allegations of physical violence against members of the press, you create an environment that only encourages this sort of nasty discord," Trump's main rival for the Republican nomination, Ted Cruz, told reporters. Throngs of protesters, many of them blacks and Latinos angered by Trump's incendiary anti-immigrant rhetoric, had massed outside and inside the venue in Chicago, mingling with the candidate's supporters. Pundits said the chaos at the rally was reminiscent of violent protests at the 1968 Democratic National Convention, also in Chicago, held when the United States was torn apart by opposing views on the Vietnam War. A Trump rally scheduled for Sunday in Cincinnati, Ohio has also been cancelled, with the local spokesman for the campaign telling US media that Secret Service supporting the campaign could not complete preparation work in time. CNN estimated there were between 8,500 to 10,000 people in the arena in Chicago when tensions erupted into chaos. The billionaire said he decided to call off the gathering after consulting with police in the city, where tensions had been rising for hours in the build-up to the event at a sporting arena at the University of Illinois at Chicago. "I don't want to see anybody hurt," Trump told CNN afterwards. "I think we made the right decision (to cancel)... even though our freedom of speech was violated." The chaos ended several hours later, but not before members of the crowd threw bottles and other objects at officers, and several tried to take the stage and speak at the podium. One sign held by a protester inside the arena said "We are not rapists," referring to Trump's characterization last year of Mexicans as rapists. - 'Address the anger together' - Police made a total of five arrests and two officers were taken to area hospitals after sustaining minor injuries, the Chicago Police Department confirmed to AFP. Critics have accused Trump of fueling the toxic atmosphere. On February 1, as protesters interrupted a rally in Iowa, he encouraged supporters to "knock the crap out of them," and pledged to pay their legal fees. When a protester disrupted Trump's speech in Las Vegas, the brash billionaire said he would like to "punch him in the face." Trump dismissed the notion that he was responsible for whipping up tensions. In a statement, Trump's campaign said he had determined that "for the safety of all of the tens of thousands of people that have gathered in and around the arena, tonight's rally will be postponed to another date." "Please go in peace," it added. Trump's rivals framed the outbreak as at least partially caused by the frontrunner's incendiary rhetoric. Candidate John Kasich, also a Republican, said that "the seeds of division that Donald Trump has been sowing this whole campaign finally bore fruit, and it was ugly." The chaotic scenes come just days before the states of Florida, Ohio, Illinois and Missouri vote in the party primaries on March 15. Many in the party see next Tuesday's votes as the last best chance to derail the insurgent candidacy of the billionaire mogul, who has so far won 15 of 24 primary races. The sudden security concerns mark a major test for Trump as he seeks to lock up the nomination and turn his attention to doing battle against Hillary Clinton, the Democratic frontrunner. Clinton was quick to strike out at Trump over the Chicago violence, releasing a statement late Friday in which she said "we all have our differences, and we know many people across the country feel angry. We need to address that anger together." After rattling the Republican establishment with his shock emergence as the man to beat, Trump has been working hard in recent days to look presidential and shake off his brash, belligerent image. But Trump's rallies are known for being rambunctious, and that seeped over into violence on Wednesday night in North Carolina when a 78-year-old white man in a cowboy hat punched a black protester in the face. Trump, who is scheduled to hold a rally Saturday in Cleveland, Ohio, has called on Republicans to amass behind him to propel him into the White House.