Barack Obama has hit out at what he calls "vulgar and divisive rhetoric" on the presidential campaign trail.

In a not-too-subtle jab at Republican front runner Donald Trump, the Democratic president called on party 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," Mr Obama said at an event on Capitol Hill on Tuesday.

"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."

He added that this year's campaign cycle was not an accurate reflection of the United States.

"It has to stop," Mr Obama said.

The President's comments come following a spate of incidents, some violent, at Trump campaign events in recent weeks.

On Monday, authorities in North Carolina said the property mogul would not be charged for inciting a riot after a protester was punched in the face by a Trump supporter at a rally.

A campaign event in Chicago was cancelled at the weekend after demonstrators clashed with Trump faithful, and in Ohio a protester was arrested after he attempted to charge the stage as Mr Trump spoke.

Mr Obama, who previously said he does not believe Mr Trump can become the Republican nominee, made his latest remarks as voters in five crucial states cast their ballots.

Mr Trump is hoping for yet another big night as he looks to distance himself from the rest of the GOP field.