In German-occupied areas they were generally interned as enemy aliens, much as happened to Axis nationals in the UK, though those on a particular nazi hate-list faced greater danger. The internment camps seem to have been more civilised affairs than those for nazism's perceived racial or ideological enemies, subject to Red Cross inspection with some inmates being released after a period of incarceration, notably men over 75 and women over 60: there's a study of women in the Besançon and Vittel camps here.