Near occupied Skadovsk, Russians have set up a camp for former Wagner private military company members, the National Resistance Centre has said on its website.
They have no support from the state and have to rely on so-called volunteers.
Wagner's men are not provided with transport or personal protective equipment. The command of the Russian occupying forces is currently deciding on their further use.
The NRC thanked the underground for providing information about Russia's actions.
In late September, Russian President Vladimir Putin instructed the former chief of staff of the Wagner PMC, Andrey Troshev, to create paramilitary units out of volunteers for the war in Ukraine.