A method for compressing gaseous fuel is disclosed. The method includes, ingesting gaseous fuel into a chamber, ingesting air into the chamber and mixing the gaseous fuel with the air, igniting and partially combusting the resulting mixture of gaseous fuel and air in a confined space such that a predominant fraction of the gaseous fuel is not combusted, causing an increased temperature and therefore an increased pressure of the fraction of the gaseous fuel which is not combusted, and discharging the resulting compressed gaseous fuel. Moreover, a compressor is provided including a casing, a rotor with at least three vanes, an inlet for gaseous fuel, an outlet for gaseous fuel, an air inlet and an igniter. The rotor is placed in the casing such that at least three variable-volume chambers part-bounded by the vanes are formed during a rotor revolution.