Comment by FatalLogic

>it seems like an obvious thing to do for both Ukrainian intelligence

Yes it must be obvious for Ukraine to use people who are already in Russia to help with local sabotage. It could be as as crude as putting rocks on a rail line or as simple as floating toy balloons across a strategic installation until the local Russian defenses get tired of the false alarms, stop paying attention and don't see an incoming drone.

It's surprising that there are apparently no strong claims of this from either side, but especially from the Russian side. I don't agree that Russia has nothing to gain from arresting people for such activities. Wouldn't it deter others?