US Republican White House frontrunner Donald Trump says he is open to harsh measures to deal with the threat from Islamic State, including going beyond the controversial interrogation tactic known as waterboarding.

In an interview on ABC America’s This Week program, Mr Trump discussed reviving the tactic and implementing other interrogation techniques, pointing to the recent beheadings of Christians in the Middle East as evidence of the need for stronger interrogation methods for suspected operatives of extremist groups.

“We’re like living in medieval times. If I have to do it and if it’s up to me, I would absolutely bring back waterboarding,” he said.

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“And if it’s going to be tougher than waterboarding, I would bring that back, too.”

When pressed by interviewer George Stephanopoulos if that meant the US employing similar methods of beheading captors, Mr Trump responded: “We’re going to do things beyond waterboarding … perhaps, if that happens to come.”

The issue of waterboarding and other methods of interrogation was raised during Saturday night’s (local time) New Hampshire Republican debate aired on ABC.

The billionaire businessman said he would not only revive the controversial method’s use, but bring back “a hell of a lot worse” if elected.

“In the Middle East, we have people chopping the heads off Christians, not since medieval times have people seen what’s going on,” he said.

“I would bring back waterboarding and a hell of a lot worse than waterboarding.”

Waterboarding is the practice of pouring water over someone’s face to mimic drowning as an interrogation tactic.

Critics say it is torture, and Democratic President Barack Obama banned use of the method days after taking office in 2009.

Mr Trump’s rival and a fellow leader in opinion polls, Senator Ted Cruz of Texas, said during the debate that he would only allow limited use of the practice but said it did not constitute torture.

‘Evil’ nature of modern times requires stronger interrogation

Waterboarding was used by the CIA under the Bush administration during the early days of the wars in Iraq and Afghanistan in the aftermath of the September 11, 2001 attacks.

Trump he would bring back waterboarding. Photo: Reuters/ABC

Its defenders say it helped to keep America safe by garnering more information from captives, but critics argued the method never actually yielded actionable intelligence.

Republicans have been critical of Mr Obama’s decision to eliminate the practice, saying it telegraphs a position of weakness to the nation’s enemies and concedes that the US erred in using waterboarding.

Mr Trump argued that the “evil” nature of modern times required more robust interrogation techniques, saying that US enemies are thriving in the absence of them.

“They laugh at us. Our enemies laugh at us, George. They say waterboarding, they don’t even think it’s a form — you know, they don’t even view that as real torture,” he said.

New Hampshire, where Mr Trump maintains a lead over Republican rivals in the US nominating contest for the November 8 election, casts its primary ballots on Tuesday, the week after Iowa kicked off the process.