Viktor Zolotov, the head of Russia's National Guard (Rosgvardia) has challenged opposition leader Alexei Navalny to a duel.
Putin's ex-head of security made the remarks in a seven-minute speech, shared on YouTube, in response to allegations from Navalny’s Anti-Corruption Foundation.
"I promise that in just several minutes I will beat you to a pulp," he threatened.
"Nobody has ever kicked your butt properly so that you’d feel it in your liver but now you came to the right person," he went on.
The Anti-Corruption Foundation published an investigative report about evidence of corruption in the Rosgvardia’s food-supply procurement contracts in August.
Putin’s spokesman, Dmitry Peskov, told reporters that Navalny’s investigation was “shameless lies” and supported Zolotov’s outburst, saying that “sometimes you need to fight shameless libel with all possible means".
The Kremlin on Tuesday dismissed suggestions that it encouraged Zolotov to make his statement.
Navalny did not respond to the challenge — he is currently serving a 30-day jail sentence for staging an illegal protest.
Here's what Zolotov said in his speech:
"You, Mr Navalny, have never had anyone fight back. You’re constantly insulting everyone, but nobody says anything in response. You know, you might be feeling like a hound following a scent or creeping up on its prey but in reality, you’re just an opposition pug-dog who thinks he’s an elephant.
“Nobody has ever kicked you butt properly. So that you’d feel it in your liver but now you came to the right person. With your speech, you made some insulting and slanderous assumptions about me.
"And, you know, among us officers, we don’t just forgive that. Since the dawn of time, they beat scoundrels and challenged them to a duel. Mr Navalny, nobody stops us from returning, at least partly, those wonderful traditions. I mean restitution. I simply challenge you to a fight – in a ring or tatami (mat) or anywhere. Where I promise that in just several minutes I will beat you to a pulp."