The story comes from The Telegraph.
Syrian Al-Qaeda group ISIS expelled from second city Aleppo
Videos posted online and reports from activists in the city said the Islamic State of Iraq and al-Sham (ISIS) fled, leaving behind hundreds of prisoners, including some who had been killed as they left.
Yusuf, a "citizen journalist" in the city, told The Daily Telegraph that 300 activists, journalists and members of other rebel groups had been freed from a makeshift jail in a former children's hospital. Some recorded harrowing accounts of their treatment in videos posted online.
"The deputy head of the Grandsons of the Prophet Brigade was imprisoned with us," said one man. "He was tortured for five days. They were asking him, 'Did you become an infidel?' He answered no, until finally under torture and humiliation he said to them, 'Yes, I became an infidel,' and then they killed him."
A broad alliance of other factions, from secular brigades originally part of the western-backed Free Syrian Army to hardline but non-al-Qaeda Islamist groups, joined together in what has every appearance of being a pre-planned sweep against ISIS a week ago.
The immediate trigger was the killing of a popular doctor who was part of a radical Salafi militia, Ahrar al-Sham, which had fought alongside both main al-Qaeda affiliates in Syria but had become disillusioned with ISIS.
ISIS have now lost control of a number of towns across the north of the country. However, they are still fighting in others. In Raqqa, the only provincial capital city in Syria entirely in rebel hands, there was said to be mayhem, with bodies left in the streets as fighting continued.
It had also spread south, one ISIS fighter from Britain said in a post on social media. The man, using the nom de guerre Abu Dujana, said he was based in Homs and that ISIS had been attacked in a "cowardly manner" by the other rebels, including groups that they had fought alongside, including Ahrar al-Sham.
He claimed that it was ISIS fighters who had been kidnapped, and their women raped.
However, he said ISIS had fought back by launching a pre-emptive attack on the other rebels. "They conspired against us in our own city and struck us so we kicked them out," he said.
The counter-attack against ISIS's increasing dominance of northern Syria is vital both to the less hardline rebels, including Islamists, who saw ISIS's behaviour driving away support for the revolution from the local population, and to their overseas backers.
Some ISIS members directly accused Saudi Arabia of organising the attack. It has promised to back the rebels and is believed to have co-ordinated a number of Islamist alliances among the rebels.
The West also want to be able to present the opposition to President Bashar al-Assad as being coherent at peace talks in Switzerland later this month.
However, if ISIS is not quickly defeated, the plan may backfire, leading to yet more internecine fighting on all fronts and a further break-up of the country into small, violent enclaves.