Republican frontrunner Donald Trump has invoked comparisons to German dictator Adolf Hitler after asking supporters to raise their right hands and pledge allegiance to him.

As he campaigned in Orlando, Florida on Saturday, the billionaire businessman asked those gathered to show their support for him and repeat a pledge.

Donald Trump makes members of his Orlando crowd raise their right hands and swear to vote in the primary. pic.twitter.com/EVenRilJrV — Jenna Johnson (@wpjenna) March 5, 2016

"Let's do a pledge. Who likes me in this room?" Trump asked those in attendance, according to footage broadcast of the event.

"Ok, I have never done this before. Can I have a pledge, a swearing? Raise your right hand. I do solemnly swear that I - no matter how I feel, no matter what the conditions, if there's hurricanes or whatever - will vote, on or before the 12th for Donald J. Trump for president," Trump said, as the attendees repeated the lines after him.

"Now I know. Don't forget you all raised your hands. You swore. Bad things happen if you don't live up to what you just did."

Photos, video and gifs of the pledge were quickly circulated on social media, with many comparing Trump to Hitler, or other dictators.

Not at all saying Trump is Hitler... But, it would be nice if he stopped the "heil" salute at his rallies. pic.twitter.com/RNq6eWcKav — Heath Mayo (@HeathMayo) March 6, 2016

Hitler: Do you swear to vote for me? Crowd: Hitler salute.

Donald Trump: Do you swear to vote for me? Crowd: Hitler salute. #SuperSaturday — John (@linnyitssn) March 6, 2016

Others, however, defended Trump - saying the frontrunner had asked for a pledge, not a salute.

Nothing to see here. Just Trump supporters making a pledge. The way the salute looks is just a coincidence... pic.twitter.com/Y5uiUHLfnv — Matt Ogle (@matt_ogle_ud) March 6, 2016

Trump was campaigning in Florida ahead of the state's all-important primary on March 15.

According to a poll average taken by RealClearPolitics, he is easily leading in the state, with 44.7 percent of the vote, ahead of Florida Senator Marco Rubio on 26 percent.

Trump's momentum was stymied somewhat on Saturday, when Texas Senator Ted Cruz beat him in Kansas and Maine, showing he may still present a challenge for the eventual Republican nomination.