A man refines oil to produce petrol and diesel. A petrol production micro-industry has grown up around the desert town of Al Mansura east of Al Raqqah, the capital of the Islamic State. Small stills burn oil that is trucked in by the barrel load from the oil fields of Al Hasakah. Each still can process about a thousand litres of crude a day into petrol and diesel. The Islamic State has taken oil fields from Syrian rebels and the government in recent months. They are believed to control hundreds of wells, an important source of income for the Islamists and depriving Syrian President Bashar al-Assad's government of a major source of income.