NH3-selective catalytic reduction (SCR) is applied worldwide to DeNOx of combustion exhausts of stationary and mobile sources, but a greater DeNOx activity at low temperatures is desired to meet forthcoming restrictive legislations and to increase energy efficiency in specific applications. We have obtained high NO reduction efficiencies at 200-300 degrees C over commercial V-based and Fe-exchanged zeolite catalysts by reacting NO with both ammonia and nitrates (e.g., ammonium nitrate) according to a novel "enhanced SCR" reaction, 2NH(3) + 2NO + NH4NO3 -> 3N(2) + 5H(2)O. This provides a new route for low-temperature NOx reduction wherein the DeNOx activity is maximized by dosing an aqueous solution of nitrates to the SCR reactor feed stream.