A gas turbine engine, especially a turbojet or turbofan for an aircraft, includes a combustion section and an exhaust section produces an exhaust gas. The emission products can be reduced by using a gas treatment device with a reactor and an injection device. The reactor produces a nitrogeneous substance such as ammonia. This reducing agent is injected in the gas phase in the exhaust section of the gas turbine engine. By selective non catalytic reaction the Nitrogen oxides of the exhaust gas can be reduced. Furthermore the injection device is arranged such that the temperature window of this reduction process is ranging from 850° C. to 1100° C. The reactor for producing gaseous ammonia can either be a thermal reactor or a high pressure plasma device.