The invention relates to a process for the combined production of a fertilizer selected from the group consisting of ammonium nitrate, ammonium phosphates or a combination thereof, by the indirect neutralization of ammonia with an acid selected from among nitric acid, phosphoric acid and a combination thereof and of a sulphur compound selected from the group consisting of elemental sulphur, SO2, sulphuric acid and sulphate salts, the claimed process consisting in contacting a sulphur oxide-containing gas, resulting from oil and coal combustion, with ammonia and an aqueous liquid, reacting the sulphur oxide-containing product resulting from the first step, with a reagent selected from nitric acid, phosphoric acid, a mixture thereof and salts formed by the reaction of said acids, and separating at least one portion of the sulphur compound from the fertilizer resulting from the second step.
