A vertical axis turbine includes a modified darrieus type rotor having at least three circumferentially spaced apart blades, each having an airfoil shape in cross section such that the blades generate a torque in a direction of rotation of the turbine about the vertical axis responsive to a generally horizontal wind across the blades. Support members, for example flexible cables, are connected under tension between adjacent ones of the blades to extend in a generally circumferential direction about the turbine at an inclination from horizontal in a criss-crossing pattern with other support members. A tensioning mechanism also urges opposing top and bottom ends of the rotor towards one another such that the blades are supported under compression in a pre-stressed condition by the support members and the tensioning mechanism to maintain the blades in a substantially rigid and fixed orientation throughout the operation of the turbine rotor.