Abstract An anomalous increase in the intensity of low-frequency (0.1–16 kHz) radiowave emissions was detected using Intercosmos 19 data when the satellite was nearly over the epicentre of an earthquake zone. Ample statistical data are the basis for a determination of the probable spatial-temporal dimensions of the region of the upper ionosphere in justify which ELF-VLF emissions were detected. The reliability of the detected phenomenon is ∼ 0.8–0.9. The ionospheric regions with the low-frequency emissions observed by Intercosmos 19 have been found to be formations (‘noise belts’) extended along ±60° of geographic longitude and ±2° of geographic latitude. The spectral characteristics of ELF-VLF emissions near seismic areas are specified. The earthquake depth and location under a continent or under an ocean has an effect on the results of the satellite observations of earthquakes. Possible mechanisms of the phenomenon are discussed.