It weights 143 kg for a change. An IED pulverizing Abrams tank weights 6,5 kg.
That IED pulverizing Abrams tank weighing 6.5 kg is very likely an EFP, not just explosives. Different thing.
143 kg equals 315 pounds for those unfamiliar with weight conversions. Depending on the version, S-300 missile warheads contain roughly 200 to 300 pounds of TNT, which is not unsubstantial. Regardless, their maximum range of 120 km means that this missile's impact point was far beyond the range of any Russian-held territory of from Belarus.
So it's Ukrainian, and either failed to self-destruct after missing a Russian missile that it was launched to intercept, or was fired in surface-to-surface mode as a deliberate false flag. Given the frequency of Ukraine's older S-300 anti-air missiles missing their targets and then falling and exploding on Ukrainian territory, my guess is that this old missile's self-destruct mechanism also failed to detonate and it flew until it ran out of fuel.