A member of the Iraqi counterterrorism forces stands by an Islamic State militants weapons factory in Falluja, Iraq, June 23, 2016. REUTERS/Thaier Al-Sudani TPX IMAGES OF THE DAY - RTX2HS5B

A view shows a school that was used by Islamic State militants as a position in the northern Syrian rebel-controlled town of al-Rai, in Aleppo Governorate, Syria, September 27, 2016. REUTERS/Khalil Ashawi - RTSPPC8

Burnt out prison cells belonging to Islamic State militants are seen in Falluja after government forces recaptured the city from Islamic State militants, Iraq, June 27, 2016. REUTERS/Thaier Al-Sudani TPX IMAGES OF THE DAY - RTX2IIXN

A Syria Democratic Forces (SDF) fighter inspects a room, which according to the SDF was used by Islamic State militants to prepare explosives, in Manbij, Aleppo Governorate, Syria, August 17, 2016. REUTERS/Rodi Said - RTX2LKTL

A tunnel used by Islamic State militants is seen in the town of Sinjar, Iraq December 1, 2015. REUTERS/Ari Jalal - RTX25ALX

Tripods and a projector are pictured inside an ancient Hammam that was used by Islamic State militants as a media centre in Manbij, in Aleppo Governorate, Syria, August 16, 2016. REUTERS/Rodi Said - RTX2LBOV

A view shows containers, which according to Syria Democratic Forces (SDF) fighters were used for making explosives by Islamic State militants, in Manbij, Aleppo Governorate, Syria, August 17, 2016. REUTERS/Rodi Said - RTX2LKTS

A view shows the institution of religious law building that was used by Islamic State militants in the northern Syrian rebel-controlled town of al-Rai, in Aleppo Governorate, Syria, September 27, 2016. REUTERS/Khalil Ashawi - RTSPPCI

A view shows car parts, which according to Syria Democratic Forces (SDF) fighters were used by Islamic State militants to prepare car bombs, at a workshop in Manbij, Aleppo Governorate, Syria, August 17, 2016. REUTERS/Rodi Said - RTX2LKTI

Weapons that belonged to Islamic State militants are seen at an Iraqi army base in Camp Tariq near Falluja, Iraq, September 4, 2016. REUTERS/Khalid al Mousily - RTX2O34Z

Explosives left behind by Islamic State militants are seen at a school, following clashes in Falluja, Iraq, June 25, 2016. REUTERS/Thaier Al-Sudani - RTX2I5X7

A factory abandoned by Islamic State militants is seen in Falluja, Iraq, June 25, 2016. REUTERS/Thaier Al-Sudani - RTX2I5Z3

A book belonging to Islamic State militants is seen in Falluja after government forces recaptured the city from Islamic State militants, Iraq, June 27, 2016. REUTERS/Thaier Al-Sudani - RTX2IIGU

Syria Democratic Forces (SDF) fighters inspect bags of niqabs at a centre that was used by Islamic State religious police (al-Hisbah) in Manbij, Aleppo Governorate, Syria, August 16, 2016. REUTERS/Rodi Said - RTX2LBSD

Image used for illustrative purpose only. Handcuffs are pictured inside a prison, which according to Syria Democratic Forces (SDF) fighters belonged to Islamic State militants, in Manbij, Aleppo Governorate, Syria, August 17, 2016. REUTERS/Rodi Said - RTX2LKTD

Homemade mortars belonging to Islamic State militants are seen in the town of Gwer northern Iraq August 31, 2016. Picture taken August 31, 2016. REUTERS/Azad Lashkari - RTX2NT6A

Members of Libyan forces allied with the U.N.-backed government neutralise explosives that they said were used by Islamic State militants, following a battle in Sirte, Libya September 5, 2016. REUTERS/Hani Amara - RTX2O8YD

An Islamic State flag hangs on the wall of an abandoned building in Tel Hamis in Hasaka countryside after the Kurdish People's Protection Units (YPG) took control of the area March 1, 2015. Kurdish forces dealt a blow to Islamic State by capturing Tel Hamis, an important town, on Friday in the latest stage of a powerful offensive in northeast Syria, a Kurdish militia spokesman said. The capture of Tel Hamis was announced by the Kurdish YPG militia and confirmed by the Syrian Observatory for Human Rights, which monitors the country's civil war. REUTERS/Rodi Said

Rocket-propelled grenades left behind by Islamic State militants are seen at a school, following clashes in Falluja, Iraq, June 25, 2016. REUTERS/Thaier Al-Sudani - RTX2I5Z5

A view shows part of a media centre that belonged to Islamic State militants inside an ancient Hammam in Manbij, Aleppo Governorate, Syria, August 16, 2016. REUTERS/Rodi Said - RTX2LBQ3

Blindfolds are pictured inside a prison, which according to Syria Democratic Forces (SDF) fighters belonged to Islamic State militants, in Manbij, Aleppo Governorate, Syria, August 17, 2016. REUTERS/Rodi Said - RTX2LKTJ

A mass grave for Islamic State militants are seen in Falluja, Iraq, September 4, 2016. REUTERS/Khalid al Mousily - RTX2O35C