The head of the Russian government's internal military force has challenged the country's best-known opposition leader to a duel.

Viktor Zolotov, a key ally of Vladimir Putin, issued the challenge in a bizarre video posted by Russia's National Guard on YouTube.

It comes after a video posted by the prominent opposition leader and Putin critic Alexei Navalny last month.

According to the Moscow Times, Mr Navalny alleged in the video investigation that leaders in the National Guard were corrupt.

In comments translated by the TASS news agency, Zolotov said: "I would like to point out that in your statement about me you spouted offensive and nasty lies. Officers never forgive such things and from time immemorial any scoundrel would earn a slap in the face and a challenge to a duel.

"Mr Navalny, it wouldn’t be such a bad thing to revive at least some of those glorious traditions. I mean getting redress. I simply challenge you to a duel, in a boxing ring, or wherever else."

He added that he would 'make a juicy steak' out of the opposition leader in a 'just a couple of minutes'.

Mr Zolotov is a long-time supporter of Vladimir Putin, and has previously worked as the Russian leader's head of security.

Anti-corruption activist Mr Navalny, meanwhile, is currently serving a 30-day prison sentence.

He has frequently been arrested for organising and taking part in protests against the Russian government.