Elon Musk has responded to an apparent threat made by the head of the Russian space agency Roscosmos, also remarking to followers that "if I die under mysterious circumstances, it’s been nice knowin ya".

The relationship between the billionaire and  Dmitry Rogozin, head of Roscosmos, has soured somewhat following the invasion of Ukraine by Russian forces, and Musk's decision to redirect Starlink satellites to support the country.

In March, Musk challenged the Russian President to single combat with the "stakes" being Ukraine, to which the increasingly erratic Rogozin responded by quoting the fairytale The Tale of the Pope and his worker Balda by A. S. Pushkin:

"You, little devil, are still young,
Compete with me weak;
It would only be a waste of time.
Overtake my brother first."

In his latest comments on Musk, Rogozin accused the world's richest man of supporting Nazis in Ukraine, a claim by Russia used to justify their invasion.

"From the testimony of the captured commander of the 36th Marine Brigade of the Armed Forces of Ukraine, Colonel Dmitry Kormyankov, it turns out that the internet terminals of Elon Musk's Starlink satellite company were delivered to the militants of the Nazi Azov Battalion and the Ukrainian Marines to Mariupol by military helicopters," the Roscosmos head wrote on his Telegram account.

"Elon Musk, thus, is involved with supplying the fascist forces in Ukraine with military communications. And for this, Elon, you will be held accountable like an adult, no matter how much you'll play the fool."

In response, Musk stated simply that "the word 'Nazi' doesn't mean what he seems to think it does".

In another tweet, he joked about dying in mysterious circumstances, a fate that seems to befall an awful lot of people who oppose the Russian president.

His mother, however, did not see the funny side.