Joe Biden has warned of a Democrat "bloodbath" as vehement supporters of his rival Bernie Sanders lash out in the wake of Super Tuesday.

Mr Biden, the new frontrunner for the Democrat nomination, had a much-needed surge in fundraising, collecting $22 million in five days after winning 10 of the 14 states that voted last week.

He expected to become the target of "Bernie Bros," hard line Sanders enthusiasts who have been accused of aggressive online behaviour.

On a phone call with supporters, Mr Biden said: "What we can't let happen is let this primary become a negative bloodbath. I know I'm going to get a lot of suggestions on how to respond to what I suspect will be an increasingly negative campaign that the Bernie Brothers will run.

"We can't tear this party apart and re-elect Trump. We have to keep our eyes on the ball in my view."

It came as Elizabeth Warren revealed that "Bernie Bros" had targeted her with hate-filled messages, including snake emojis, urging her to drop out of the race.

Ms Warren has now ended her campaign but did not immediately endorse another candidate, despite being from the same wing of the party as Mr Sanders, and the pair being friends of long standing.

She accused Mr Sanders' supporters of posting online the home addresses of women who had endorsed her, and subjecting them to an "onslaught of online threats."

Ms Warren said: "I think there’s a real problem with online bullying and online nastiness. I’m not just talking about who said mean things, I’m talking about some really ugly stuff that went on."