CoxMn3-xO4 oxides (0 <= x <= 3) were prepared by controlled decomposition of mixed oxalates near 200 degrees C, followed by a calcination at 300 degrees C. These oxides are amorphous for x <0.9. For higher cobalt fraction they have a cubic spinel structure and their crystallite size grows with the cobalt fraction. These materials have a large surface area; the highest values, exceeding 250 m(2)/g, were obtained for x approximate to 2. The spinel oxides exhibit an outstanding catalytic activity for propane oxidation at mild temperature (20-200 degrees C). They are also active for CO oxidation at ambient temperature. This high activity was correlated both with the surface area and the cobalt concentration. The most efficient material is Co2,3Mn0.7O4, which has a better activity than cobalt oxide catalysts reported in the literature. (C) 2015 Elsevier B.V. All rights reserved.