The first showed a photograph of a blindfolded man having his arm positioned on a table by fighters as a masked man wielding a sword waits nearby. Another man, wearing a white robe of the kind favored in Arab Gulf countries, is reading a statement. A caption states that the blindfolded man is a thief who had asked to have his hand cut off "in order to cleanse his sins."
A second photograph was taken just as the sword is about to strike the hand while a burly fighter restrains the victim.
A third picture posted an hour later is too graphic to show here. The man appears to be passed out, with his bloodied arm and his severed hand resting on the table. Fresh slashes in the wood suggest it took four swipes of the sword to cut the hand off.
[UPDATE: The Twitter account that posted the photos, @reyadiraq, has been suspended. When asked why, a Twitter spokesperson said the company doesn't comment on individual accounts and pointed to the rules and media policy. A screengrab of the first photo is at the top of this post. The account had about 96,000 followers and more than 20,000 tweets before suspension.]
ISIS evolved from the al-Qaeda-affiliated Islamic State of Iraq, which U.S. forces battled to contain before they withdrew in 2011. The group's attempts to impose strict interpretations of Islamic law on the parts of rebel-held northern Syria under its control have earned it many enemies.
Mainstream Free Syrian Army fighters declared war on the group in January and ejected its fighters from several locations. Earlier this month, al-Qaeda's central command issued a statement dissociating the organization from ISIS, suggesting its methods were too harsh even for al-Qaeda to stomach. On Tuesday, al-Qaeda's official Syrian affiliate, Jabhat al-Nusra, gave ISIS an ultimatum threatening war unless ISIS submits to arbitration of its disputes with other rebels.
Under pressure, ISIS on Friday pulled out from the northern town of Azaz. A video posted on YouTube showed scenes of celebration among residents.