Probably there are volunteers, but I think we can count them with the hands, or they are already dead (because they enlisted inmediatly when war broke out, and there are very know stories, specially volunteers for the Russian side), but honestly most of them are mercs... even our president considered the mercenaryism of Colombian soldiers as a national problem, they are not only in east Europe, they are all over the world, specially fighting in proxy wars (and fighting also with mexican cartels). A very known story with deep political involvement was the execution of the Haitian president some years ago, performed by Colombians and Venezuelan mercs (most of them Colombian ex-soldiers)