A process for treating a gas containing hydrogen sulphide (H.sub.2S) and sulphur dioxide, contacting the gas at a suitable temperature with an organic solvent containing at least a soluble catalytic system, comprising at least one compound comprising at least one functional group A consisting of a carboxylic acid function and at least one functional group B comprising at least one nitrogen atom and which can produce an acid-base type reaction with at least one functional group A under the operating conditions of said process; and recovering a gaseous effluent substantially depleted in hydrogen sulphide and sulphur dioxide along with liquid sulphur separated from the solvent by liquid-liquid decantation.