Abstract: A combustion process for nitrogen- or for sulphur- and nitrogen-bearing fuels wherein fuel combustion is divided, by staged oxygen (preferably in the form of air) injection, into at least two combustion zones. The first combustion zone involves providing fuel-rich stoichiometric conditions under which nitrogen chemically bound in the fuel (i.e. fuel-bound nitrogen) is substantially converted to molecular nitrogen. The second (final) combustion zone comprises at least two stages. In the first stage of the final combustion zone, combustion products from the first combustion zone are further conbusted under a condition of fuel-rich stoichiometry, preferably at an oxygen/fuel stoichiometric ratio of from about 0.08 to about 1.0 and at a temperature of less than about 2200 K. In the second stage of the final combustion zone, combustion products from the first stage are combusted at an oxygen/fuel stoichiometric ratio of greater than about 1.0 and at a temperature of less than about 1500 K.