Media playback is unsupported on your device Media caption How Trump deals with rally protesters

The US Republican presidential front-runner, Donald Trump, has cancelled a rally in Chicago because of angry protests at the venue.

It is not the first time that things have turned nasty at a Trump campaign event.

When asked about it at a debate on Thursday, Mr Trump blamed unruly protesters for the violence.

Speaking after Friday night's scuffles, his rival for the nomination, Ted Cruz, said Mr Trump was responsible.

"When you have a campaign that affirmatively encourages violence... you create an environment that only encourages this sort of nasty discourse," the Texas senator said.

Here are some of the most recent incidents - and how Mr Trump has responded.

Chicago, Illinois, 11 March

Image copyright AP

What happened: Fighting broke out between Trump supporters and protesters at the venue before Mr Trump was due to speak. The campaign decided to postpone the event, and there were more scuffles.

What Mr Trump said: Mr Trump told MSNBC that he cancelled the rally because he "didn't want to see anybody get hurt".

He later told CNN that he had no regrets about his rallies, describing the protesters as "bad dudes". "They were rough, tough guys," he added.

St Louis, Missouri, 11 March

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What happened: Protesters repeatedly interrupted Mr Trump's speech at a rally in Missouri. More than 30 people were arrested.

What Mr Trump said: "They're allowed to get up and interrupt us horribly and we have to be very, very gentle. They can swing, they can hit people but if we hit them back it's a terrible, terrible thing."

Fayetteville, North Carolina, 9 March

Media playback is unsupported on your device Media caption Footage shows a Trump supporter punching a protester at a Trump rally

What happened: Video footage from a rally showed a Trump supporter punching a black protester in the face as he was led away. A 78-year-old man has been charged with assault.

What Mr Trump said: "Uh oh, so early. So early. Alright, get him out, thank you. We're gonna have such fun, such fun tonight," Mr Trump said from the podium, though he is unlikely to have seen the punch thrown.

Later in the same speech he said of protesters: "They put their hand up and they put the wrong finger in the air... and they get away with murder. Because we've become weak."

Warren, Michigan, 4 March

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What happened: Mr Trump reportedly encouraged people at the rally in Warren to get rid of a protester who had interrupted him.

What Mr Trump said: "Get him out. Try not to hurt him. If you do I'll defend you in court," the contender said, according to CBS.

Las Vegas, Nevada, 22 February

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What happened: A protester was escorted out of a Trump rally on the eve of the Nevada caucuses while the billionaire was addressing the crowds.

What Mr Trump said: "I'd like to punch him in the face, I'll tell you," Mr Trump said. "You know what they used to do to guys like that when they were in in a place like this?" Mr Trump asked. "They'd be carried out on a stretcher, folks."

Cedar Rapids, Iowa, 1 February

Image copyright Getty Images Image caption No tomatoes were thrown at the rally in Cedar Rapids

What happened: Mr Trump had apparently been warned by his security staff that there could be someone in the audience with tomatoes.

What Mr Trump said: ""If you see somebody getting ready to throw a tomato, knock the crap out of them, would you?" Mr Trump told his supporters at the rally. "I promise you, I will pay for the legal fees."

Birmingham, Alabama, 21 November

What happened: A Black Lives Matter protester who disrupted a Trump speech at a rally was assaulted by a group of white Trump supporters. The protester also claimed that the assailants used the N-word.

What Mr Trump said: While his campaign was quick to condemn the violence, Mr Trump told Fox News that the protester was obnoxious and loud, adding: "Maybe he should have been roughed up because it was absolutely disgusting what he was doing."