Obama: vicious tone and violence on campaign trail have to stop

President Barack Obama said on Tuesday he was dismayed by what was happening on the U.S. presidential campaign trail and, in a reference to Republican front-runner Donald Trump, called on leaders to reject violence and clean up the tone of the race.

"We have heard vulgar and divisive rhetoric aimed at women and minorities, at Americans who don't look like us or pray like us or vote like we do," Obama said during an event on Capitol Hill.

"We've seen misguided attempts to shut down that speech. However offensive it may be, we live in a country where free speech is one of the most important rights that we hold. In response to those attempts, we've seen actual violence. And we've heard silence from too many of our leaders."

Obama spoke as Americans in five important states - Ohio, Florida, Illinois, Missouri and North Carolina - voted in primaries to select the Democratic and Republican presidential candidates for the November election.

The president has said previously he did not believe Trump, the brash billionaire who has catapulted to the lead of the Republican race for the White House, would win in November if he becomes the party's nominee.

But Obama's latest comments reflected the degree to which recent violence on the campaign trail, primarily at Trump rallies, has prompted him to step up his own rhetoric in response.

Trump, 69, has characterized Mexican illegal immigrants as criminals and proposed a temporary ban on Muslims entering the United States.

Obama said he rejected any effort to spread fear or encourage violence and said this year's campaign cycle was not an accurate reflection of the United States.

"It has to stop," Obama said, describing the atmosphere of the campaign as "vicious."

U.S. Senators Ted Cruz of Texas and Marco Rubio of Florida and Governor John Kasich are challenging Trump for the nomination.

"I suspect that all of us can recall some intemperate words that we regret. Certainly I can," Obama said. "And while some may be more to blame than others for the current climate, all of us are responsible for reversing it."