The group called on Ukraine's government to follow through with a commitment made earlier this month not to employ such weapons.
An ally of Russian President Vladimir Putin said that the Wagner mercenary group only advanced so quickly because all of Russia's forces were focused on defending Moscow.
One man who declined to be named at all said he thought it was just politics playing out.
Chaos in Moscow or a civil conflict could lead to worse casualties and also put in danger the nuclear weapons that Russia possesses.
Ukraine advances forces near Bakhmut • Ukrainian officials say "chaos in Russia" works to their advantage
In an official statement from the Russian Prosecutor-General’s Office, Moscow claimed that WWF was trying to undermine and sabotage Russia's development in the Arctic.
The ministry said this was part of a wider reward scheme under which more than 10,000 Russian servicemen had received individual bonuses.