WASHINGTON • Islamic State in Iraq and Syria (ISIS) has set up departments to handle "war spoils", including slaves, and the exploitation of natural resources such as oil, creating the trappings of government that enable it to manage large swathes of Syria and Iraq and other areas.

The hierarchical bureaucracy, including petty rivalries between officials, and legal codes in the form of religious fatwas are detailed in a cache of documents seized by US Special Operations Forces in a May raid in Syria that killed top ISIS financial official Abu Sayyaf.

US officials say the documents have helped to provide insight into how a once small insurgent group has developed a complex bureaucracy to manage revenue streams and oversee subjugated populations.

"This really kind of brings it out. The level of bureaucratisation, organisation, the diwans, the committees," Mr Brett McGurk, President Barack Obama's special envoy for the anti-ISIS coalition, said. For example, one diwan, roughly equivalent to a government ministry, handles natural resources, including the exploitation of antiquities from ancient empires. Another processes "war spoils," including slaves.

"(ISIS) is invested in the statehood and Caliphate image more so than any other jihadist enterprise. So a formal organisation, besides being practical when you control so much contiguous territory and major cities, also reinforces the statehood image," said Mr Aymenn al-Tamimi, a fellow at the Middle East Forum think tank.

The documents also show how "meticulous and data-oriented" ISIS is in managing the oil and gas sector, although it is not a sophisticated operation, said Mr Amos Hochstein, the State Department's top official for energy affairs.

Reuters could not independently verify the authenticity of the documents it obtained, which represent a fraction of the material seized in the Syria raid. Many of the seized documents are fatwas, or religious rulings, covering issues from rape of female prisoners to when it is permissible for a son to steal from his father to fund travel to fight holy war.

REUTERS