This invention relates to the production of synthesis gas by partial oxidation of liquid or gaseous, carbonaceous fuel in the presence of an oxygen-containing oxidant, wherein the fuel, the oxidant and a moderator are separately supplied to a burner and wherein the fuel and the moderator are mixed in a mixing chamber of the burner, before they are brought in contact with the oxidant. To reduce the load of the burner in particular during operation with transient conditions, the oxidant is centrally introduced through an outlet opening of the burner into a combustion chamber and the mixture of fuel and moderator is introduced through the outlet opening into the combustion chamber concentrically around the oxidant.