The present invention relates to a process for producing a hydrogen containing gas mixture comprising the following steps: (i) providing a preheated mixture comprising a fossil fuel, preferably methane, and steam, (ii) conducting an adiabatic reaction between the fossil fuel and the steam, in the presence of a catalyst, wherein a first reaction product mixture is formed comprising methane, hydrogen and carbon dioxide, and (iii) conducting an oxygen-assisted reforming reaction in the presence of a catalyst between said first reaction product mixture and an oxygen comprising stream, wherein the oxygen comprising stream comprises at least 40 vol % oxygen, forming a second reaction product mixture comprising hydrogen and carbon monoxide. The invention also relates to a system suitable for hydrogen production from a hydrocarbon feed according to the present invention.