An internal combustion engine having a main combustion chamber connected to an intake port for an air-fuel mixture, and an auxiliary combustion or a precombustion chamber communicated with the main combustion chamber through a plurality of torch apertures. The auxiliary combustion chamber is, before a combustion stroke of the engine, supplied through the torch apertures with an amount of the mixture for pre-combustion therein. A spark plug has a set of electrodes disposed in at least one of the torch apertures for causing the pre-combustion of the mixture in the auxiliary combustion chamber to thereby generate torch jets which are directed into the main combustion chamber to ignite the mixture therein. The torch apertures are arranged such that the residual combustion gases produced during a combustion stroke of the engine and retained in the auxiliary combustion chamber are forced out therefrom through at least one of the torch apertures during a succeeding intake stroke, due to the mixture flowing into the auxiliary combustion chamber through the other torch aperture or apertures.