We show results of an analysis of high-frequency pulses observed by the HF instrument on-board the DEMETER satellite. These broadband pulses extend typically from a lower frequency cutoff up to the upper frequency limit of the HF instrument (3.3 MHz). We can observe them only during the night-time since during the day-time the cutoff frequency is above the upper frequency limit of the HF instrument. These signatures are mostly observed above thunderstorms regions in the southern hemisphere. We have composed a database of these events observed during whole DEMETER mission (2004-2010). For several events observed during the burst mode, we show connection between lightning discharges and HF signatures based on the plane wave analysis of the waveforms in the ELF/VLF range. We also use a reverse ray tracing method for calculation of the expected ray path between the causative lightning discharges and satellite position. This method is based on the IRI2007 density model and shows limits for propagation of these signals through the ionosphere.