A drive system for a vehicle comprises two electrical machines arranged between a combustion engine and an input shaft to a gearbox. The first electrical machine rotor is connected with a planetary gear component, and the input shaft of the gearbox is connected with another planetary gear component. The second electrical machine rotor is connected via a transmission with the output shaft of the combustion engine, which is connected with another planetary gear component. A first locking means may be moved between a locked position, wherein the planetary gear's components rotate at the same rotational speed, and a release position wherein the components rotate at different rotational speeds. A second locking means may be moved between a locked position, and a release position wherein the output shaft of the combustion engine is locked in the locked position and disconnected in the release position with said additional planetary gear component.