Russia's FSB security service has opened a criminal case against Yevgeny Prigozhin, head of Russia's Wagner private military group, for calling for armed mutiny, Russian media reported on Friday, citing the National Antiterrorism Committee.

Prigozhin on Friday accused the Russian military of "destroying" his fighters, without fully explaining his accusation, and vowed to stop what he called the "evil" of the military leadership.

The Russian Defense Ministry has denied reports circulating on social media that the Russian Armed Forces carried out strikes on Wagner encampments and urged Wagner fighters to "stop the columns" and return to their deployment points.

Security has been stepped up around Moscow and in the city of Rostov near southeast Ukraine, Russian state media reported early on Saturday.

Russian Prosecutor-General Igor Krasnov has informed President Vladimir Putin about the criminal case against Prigozhin, TASS news agency reported citing Kremlin spokesman Dmitry Peskov. It added that senior Russian officials from the FSB as well as the defense and interior ministries are reporting to Putin on measures they are taking in response to the call for mutiny.