"I don't think our supporters are inciting. What our supporters are doing is responding to a candidate who has, in fact, in many ways, encouraged violence," Sanders said Saturday at a press conference in Chicago. "When he talks about ... 'I wish we were in the old days when you could punch somebody in the head.' What do you think that says to his supporters?"
Sanders also referred to an incident earlier this week in which a black protester was sucker-punched
by a Trump supporter as he was being led out of a rally.
"So the issue now is Donald Trump has got to be loud and clear and tell his supporters that violence at rallies is not what America is about and to end it," Sanders said.
At a campaign event in Dayton, Ohio, on Saturday, Trump accused Sanders supporters -- some of whom chanted the senator's name at the Chicago rally on Friday after it was canceled -- of helping incite violence.
"Some represented Bernie, our communist friend," Trump said.
At a rally in Cleveland later Saturday, Trump doubled down on his accusation when a protester disrupted his event moments after it began.
"You know Bernie was saying Mr. Trump should speak to his crowd," Trump said. "You know where they come from? Bernie's crowd. They're Bernie's crowd," Trump said to cheers from the crowd.
Later at the Cleveland rally, Trump mocked Sanders over an incident last year
in which Black Lives Matter protesters confronted Sanders at a campaign event and pressured him into leaving the podium to allow them to speak. Mimicking Sanders, Trump slumped his shoulders, turned around, and danced away from the podium.
And when a protester momentarily disrupted Trump's rally, the GOP front-runner again said the demonstrator was a "Bernie person."
"Get your people in line, Bernie," Trump said.
MoveOn.org, a leading progressive group that has endorsed Sanders
, confirmed in a statement that it helped students print signs for the protests at the Chicago rally and recruit members to attend the "student-led protest." But it said the protest was the "direct result of the violence that has occurred at Trump rallies and that has been repeatedly encouraged by Trump himself from the stage."
The Sanders campaign said there was no evidence any Sanders campaign staff was involved in organizing the protests, and Sanders did not apologize on Saturday for the unrest.
In a statement issued later Saturday, Sanders added: "As is the case virtually every day, Donald Trump is showing the American people that he is a pathological liar."
Trump's campaign postponed the Chicago rally amid fights between supporters and demonstrators, protests in the streets and concerns that the environment at the event was no longer safe.
Hundreds of demonstrators packed into an arena, breaking out into protest even before Trump had shown up. At least five sections in the arena were filled with protesters.
The cancellation, which came amid large protests both inside and outside the event at the University of Illinois at Chicago, follows heightened concerns about violence in general at the GOP front-runner's rallies.