An invigorated Donald Trump will appear at a handful of rallies Sunday despite a climate of growing tension, as his White House rivals warn that the Republican's heated rhetoric is fanning dangerous flames.

The brash billionaire, who is leading the race for his party's presidential nomination in spite of incendiary rhetoric and hostile remarks towards immigrants and Muslims, is scheduled to jet between three rallies in Illinois, Ohio and Florida.

The states are among five that will hold nominating races in next Tuesday's crucial round of votes, which also includes Missouri and North Carolina.

The key elections are expected to further winnow the Republican field, with Florida Senator Marco Rubio and Ohio Governor John Kasich both facing make-or-break tests in their home states.

Although Trump is ahead in national polls and his party's delegate count, he was sorely defeated Saturday in nominating contests in the US capital of Washington, DC and Wyoming by rivals Rubio and Ted Cruz respectively.

The defeats do not majorly undermine Trump, however, whose rallies have increasingly become the scene of clashes between supporters and protesters offended by his abrasive speech.

On Friday, the violence peaked as Trump called off a rally in Chicago where scenes of chaos erupted as people threw bottles and punches. At least five people were arrested.

But Trump dismissed the notion Saturday that his extreme statements on immigrants and Muslims had exacerbated tensions, placing the blame squarely on "organized thugs" as he returned to the theme over and over on the campaign trail.

Without mentioning Trump's name directly, US President Barack Obama gave a mocking rebuke of the Republican at a Democratic party fundraising event in Dallas on Saturday.

"We are great right now," Obama retorted, in remarks that played on Trump's campaign slogan of "Make America great again."

"What the folks who are running for office should be focused on is how we can make it even better -- not insults and schoolyard taunts and manufacturing facts, not divisiveness along the lines of race and faith. Certainly not violence against other Americans," Obama said.

Democratic frontrunner Hillary Clinton issued a stern warning as well.

"If you play with matches, you're going to start a fire you can't control. That's not leadership, that's political arson," Clinton said.

Early Saturday a demonstrator tried to rush on stage during Trump's rally in Dayton, Ohio, leading the candidate to make unverified claims that the man was linked to the Islamic State group.

"So, the judge let him go. And then one of my people said, wow. They found his name, and it was probably ISIS or ISIS related. Do you believe it? Certainly, he's not in love with our country, that I can tell you, okay?" Trump said.

According to the Dayton Daily news website, the man in question is a 22-year-old anti-racism activist named Thomas Dimassimo, who was filmed last year taking part in a protest that involved students standing on American flags, holding signs saying, "Not my flag."

In support of his claim, Trump tweeted a link to a video of the flag protest, dubbed over with Islamic chants in what appeared to be a crude hoax intended to suggest ties to extremism.

Trump hosted two huge meetings Saturday in the heartland state of Ohio and one in Kansas, which passed without major troubles, but in a climate of palpable tension with groups of protesters picketing the various venues.

In Cleveland, protesters gathered outside the cavernous exhibition center hosting Trump's rally holding signs that read "Dump Trump!," and "Donald Trump: Making America Hate Again."

Half a dozen police on horseback watched from a distance a heated verbal exchange between several black protesters and mostly white
Trump supporters who yelled in their faces: "Get a job! Get a job!"

The evening rally in Kansas City was repeatedly disrupted by protests.

"Get 'em out," Trump said. "I hope they arrest these people, because they're really violating all of us, okay?" he said, vowing to press charges.