An internal combustion engine includes one main combustion chamber for the combustion of a first combustion mixture, one pre-combustion chamber for each respective main combustion chamber for the combustion of a second combustion mixture, a first fuel gas mixer for providing the first combustion mixture, a second fuel gas mixer for providing the second combustion mixture, an air feed line and a synthesis gas feed line, a first mixture line connected to the first fuel gas mixer and the main combustion chamber, and a second mixture line connected to the second fuel gas mixer and the pre-combustion chamber. The first fuel gas mixer is connected to the synthesis gas feed line for the admixing of synthesis gas, and an open or closed loop control device is provided for open or closed loop controlling mixing ratios of fuel, air and synthesis gas in the first combustion mixture and/or second combustion mixture.