Donald Trump in Iowa
GOP frontrunner candidate Donald Trump talks tough in Iowa.Reuters

Republican frontrunner Donald Trump made his last speech before the Iowa caucuses memorable. He urged supporters to beat up protesters at his rally.

"If you see somebody getting ready to throw a tomato, knock the crap out of them," Trump said in Cedar Rapids after warning of opponents in the crowd. "Seriously. Okay? Just knock the hell — I promise you, I will pay for the legal fees. I promise, I promise. It won't be so much 'cause the courts agree with us, too."

He said he had been tipped off about possible protesters by the "wonderful security guys" on the scene, reported Time magazine.

Trump soon spotted a heckler and ordered him removed before the protester could be attacked. The previous week a heckler who lobbed at least one tomato at Trump — and missed — was arrested for disorderly conduct.

US election 2016: Guide to the Republican candidatesIBTimes UK

At a rally in November 2015, some of Trump's supporters clashed violently with a protester wearing a #Black Lives Matter T-shirt. When the man disrupted the candidate's speech in Birmingham, Alabama, he was shoved, punched and kicked. Police removed the protester from harm and his attackers were ordered to leave.

A Trump spokesman said then that the campaign "does not condone this behavior." But Trump noted later in an interview on Fox News: "Maybe he should have been roughed up." He said the protester was "so obnoxious and loud," and what he was doing was "absolutely disgusting."

Trump was heading into the caucuses with a seven-point lead over his closest GOP rival, Ted Cruz.