Washington (CNN) When it comes to his assessment of world leaders, Sen. Marco Rubio isn't pulling any punches: Russia's run by a "gangster" and North Korea a "lunatic."

The 2016 Republican presidential candidate made a foreign policy speech Friday morning in South Carolina, in which he riffed on his unvarnished opinions on various enemies of the United States.

His harshest words were reserved for Russian President Vladimir Putin.

"Russia is governed today by a gangster," Rubio said. "He's basically an organized crime figure who controls a government and a large territory. ... This is a person who kills people because they're his political enemies. If you're a political adversary of Vladimir Putin, you wind up with plutonium in your drink or shot in the street."

He also called Russia one of the top five threats to the United States, saying "we have a gangster running the largest nuclear stockpile in the world."

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