The Moscow region has suspended all mass outdoor events until 1 July, the authorities announced.
It follows the mayor telling everyone to refrain from travelling around the city.
Sergei Sobyanin earlier put out a statement on Telegram announcing that “a counter-terrorist operation regime has been declared in Moscow” and that Monday will be a “non-working day” to “minimise risks”.
He asked Muscovites to “refrain from travelling around the city as much as possible”.
“City services are on high alert,” he said.
Wagner mercenaries appear to be moving north from central regions of Russia, in the direction of the capital.