An axial swirler, in particular for premixing of oxidizer and fuel in gas turbines, includes a series of swirl vanes with a streamline cross-section. Each swirl vane has a leading edge, a trailing edge, and a suction side and a pressure side extending each between the leading and trailing edges. The swirl vanes are arranged around a swirler axis, wherein the leading edges extend essentially in radial direction. Flow slots are formed between the suction side of each swirl vane and the pressure side of its nearest neighboring swirl vane. Furthermore, at least one swirl vane has a discharge flow angle between a tangent to its camber line at its trailing edge and the swirler axis that is monotonically increasing with increasing radial distance from the swirler axis. The invention also relates to a burner with such a swirler and a method of operating the burner.