If a nuke detonates in any location other than Kiev, then we can definitively claim it to be a NATO nuke. Putin isn't dumb enough to risk using nukes without using them to irradiate the entire country of Ukraine. If the Russians use nukes it will be to prevent NATO forces from traveling through, and using Ukrainian territory to invade Russia. The entire country of Ukraine will have a radioactive glow that will last for hundreds of years, and become impassible terrain.
If a nuke detonates in any location other than Kiev, then we can definitively claim it to be a NATO nuke. Putin isn't dumb enough to risk using nukes without using them to irradiate the entire country of Ukraine. If the Russians use nukes it will be to prevent NATO forces from traveling through, and using Ukrainian territory to invade Russia. The entire country of Ukraine will have a radioactive glow that will last for hundreds of years, and become impassible terrain.