Former Florida Gov. Jeb Bush and billionaire Donald Trump tore into each other during the ninth Republican primary debate Saturday, issuing sharp critiques of each other's plans to address the rising threat of Islamic terrorism.

Seconds after Bush outlined his strategy to defeat the Islamic State, which emphasizes military buildup and the creation of a Sunni-led coalition in the Middle East, Trump interjected to decry the Florida Republican's foreign policy.

"Let me just tell you this: Jeb is so wrong," the businessman said. The remark drew heavy boos from the audience, prompting Trump to claim, "those are Jeb's special interests and lobbyists talking.

"Jeb is so wrong," he repeated, shortly after the crowd finished booing him. "You got to fight ISIS first.

"Right now, you have Russia and you have Iran, you have them with [Syrian President Bashar] Assad and with Syria. You have to knock out ISIS," Trump continued. "They're chopping off heads – these are animals. You have to knock them out, you have to knock them out strong. You decide what to do after, [but] you can't fight two wars at one time."

He added, "If you listen to [Bush] and you listen to some of the folks that I've been listening to, that's why we've been in the Middle East for 15 years and we haven't won anything.

"We've spent $5 trillion..." Trump said, before being interrupted again by a crowd that audibly disagreed with him.

"I only tell the truth, lobbyists," he shot back sharply. "We have to rebuild our country, we have to rebuild our infrastructure. [If] you listen to [Bush] you're going to be there another 15 years."

Bush shot back, criticizing the simplicity of Trump's strategy and slamming his opponent's praise of Russian President Vladimir Putin, who recently called Trump a "genius."

"The very basic fact is Vladimir Putin is not going to be an ally of the United States; the whole world knows that," Bush said. "They're not even attempting to take out ISIS. They're attacking the troops that we're supporting. We need to create a Sunni-led coalition to destroy ISIS and bring about stability and you can't do that with Assad in power."

"We have troops we don't even know who we're supporting," Trump said, to which Bush responded with a sharp one-liner: "This is a guy who gets his foreign policy from listening to the shows."