The clashes in Deir el-Zour province, which borders Iraq, are part of broader rebel-on-rebel clashes that have raged across opposition-held northern Syria since early January. The violence pits rebel groups, including the al-Qaida-affiliated Nusra Front, against the Islamic State of Iraq and the Levant, which was disavowed by the terrorist network earlier this year because of its brutality.
This war-within-a-war has been a massive drain on resources and manpower on the opposition in Syria, undermining its fight against President Bashar Assad in the wider civil war. Since January, more than 6,000 people have been killed in the infighting, according to activists.
Once spread across much of northern Syria, the Islamic State withdrew many of its far-flung fighters to its stronghold in the northern city of Raqqa earlier this year after other rebel factions, furious with the Islamic States' efforts to impose its hard-line interpretation of Islam, launched an offensive against the group.
But the Islamic State since has consolidated its hold on Raqqa and the surrounding province. Then in early May, its fighters pushed onward to the neighbouring province of Deir el-Zour, capturing villages and towns along the Euphrates River and closing in on the provincial capital, the city of Deir el-Zour.
A police official in Damascus said an unknown number of prisoners were released today from the Adra prison northeast of the capital.
Observatory director Rami Abdurrahman confirmed that some people were freed in Adra as well as in Aleppo, but said "we don't know exactly how many have been released up till now.
