Biogases such as natural gas and other gases capable of being biologically derived by digestion of organic matter are converted to a clean-burning hydrocarbon liquid fuel in a continuous process wherein a biogas is fed to a reaction vessel where the biogas contacts a liquid petroleum fraction and a transition metal catalyst immersed in the liquid, vaporized product gas is drawn from a vapor space above the liquid level, condensed, and fed to a product vessel where condensate is separated from uncondensed gas and drawn off as the liquid product fuel as uncondensed gas is recycled to the reaction vessel.