Insight - Islamic State turns radical Islam on Syria Muslims

An Islamic State militant uses a loud-hailer to announce to residents of Taqba city that Tabqa air base has fallen to Islamic State militants, in nearby Raqqa city August 24, 2014. REUTERS/Stringer

BEIRUT (Reuters) - As Islamic State militants advanced in the Syrian province of Deir al-Zor last month, those who had held out against them faced a simple choice: beg for mercy or face certain death.

Their options were laid out in stark religious terms by the militant Islamists who are trying to carve out their own state in Syria and Iraq. Defeated fighters were required to "atone" or die, a choice set out in Islamic terms and implying that resisting Islamic State rule amounted to a sin against God.