A burner installable to a furnace for burning an air-fuel mixture and for generating a flame in the furnace, said burner comprising a frame member provided with an elongated combustion head protruding from said frame member and being adaptable inside the furnace, what in a view from the burner's frame member is a distal end of said combustion head being adaptable to generate both a main flame and a primary flame, said combustion head comprising an outer, larger diameter channel for a mixture of combustion air and fuel, as well as a smaller diameter, inner channel, surrounded by said outer channel, for primary air as well as for primary gas, whereby the inner channel extends from the burner's frame member to the distal end and comprises an inner tube (4, 41) for primary gas and an outer tube (4; 42) surrounding said inner tube (4; 41), wherein a flow space (4; 43) for primary air is provided between the outer side of a jacket of said inner tube and the inner side of a jacket of the outer tube (4; 42), and which combustion head's outer channel extends from the burner's frame member to the combustion head's distal end and can be provided with a supply of premixed air-fuel mixture from the burner's frame member, or from that section of the combustion head which is associated with the frame member and located, in the flowing direction of the premixed air-fuel mixture, upstream of a combustion chamber, for generating the main flame B), wherein the space delimited by the outer wall of the outer channel and the jacket of the outer tube of the inner channel is constructed as a discharge channel extending from the frame member to the distal end of the combustion head, whereby the discharge end of said discharge channel is veered away from the longitudinal center line of the combustion head so that the center line of said discharge end, or an extension thereof, forms an inclined angle of incidence (t) with the combustion head's longitudinal center line, said angle of incidence (t) being 90-140 degrees as said discharge end of the discharge channel is viewed from the direction of the burner's frame member, a flow controller is provided in the flow space (4; 43) for primary air, at the distal end of the combustion head, for directing the flow of primary air in the flow space so that the primary air flows from the flow controller towards the mouth of the flow space, in the vicinity of the jacket of the outer tube (4; 42) of the inner channel, a plurality of nozzles is provided in the inner tube (4; 41) of the inner channel, at the distal end of said inner tube in the flowing direction of the primary gas, for directing the primary gas into the flow space (4; 43), either upstream or downstream of the flow controller in the flowing direction of the primary air. the inner channel extends from the burner's frame member to the distal end and comprises an inner tube (4, 41) for primary gas and an outer tube (4; 42) surrounding said inner tube (4; 41), wherein a flow space (4; 43) for primary air is provided between the outer side of a jacket of said inner tube and the inner side of a jacket of the outer tube (4; 42), and which combustion head's outer channel extends from the burner's frame member to the combustion head's distal end and can be provided with a supply of premixed air-fuel mixture from the burner's frame member, or from that section of the combustion head which is associated with the frame member and located, in the flowing direction of the premixed air-fuel mixture, upstream of a combustion chamber, for generating the main flame B), wherein the space delimited by the outer wall of the outer channel and the jacket of the outer tube of the inner channel is constructed as a discharge channel extending from the frame member to the distal end of the combustion head, whereby the discharge end of said discharge channel is veered away from the longitudinal center line of the combustion head so that the center line of said discharge end, or an extension thereof, forms an inclined angle of incidence (t) with the combustion head's longitudinal center line, said angle of incidence (t) being 90-140 degrees as said discharge end of the discharge channel is viewed from the direction of the burner's frame member, a flow controller is provided in the flow space (4; 43) for primary air, at the distal end of the combustion head, for directing the flow of primary air in the flow space so that the primary air flows from the flow controller towards the mouth of the flow space, in the vicinity of the jacket of the outer tube (4; 42) of the inner channel, a plurality of nozzles is provided in the inner tube (4; 41) of the inner channel, at the distal end of said inner tube in the flowing direction of the primary gas, for directing the primary gas into the flow space (4; 43), either upstream or downstream of the flow controller in the flowing direction of the primary air.