Low-frequency density fluctuations in the outer region of the TORTUR Tokamak are observed by microwave scattering. The frequency spectrum, measured for a fixed wave vector, is very broad and can be explained by drift waves, predominantly of the collisionless types. A considerable enhancement of this kind of turbulence is found after the application of fast high-voltage current pulses on top of the current plateau, showing a proportionality with the square of the plasma current.