The US has negotiated support from ten Arab states to help them tackle the threat of the Islamic State (formerly ISIS) in Iraq, Syria, and elsewhere.
Hassan Abboud and around 20 other top commanders from the Islamist rebel group Ahrar Ash Sham have been killed in a suicide bomb blast.
The US has confirmed that video showing the killing of reporter Steven Sotloff is authentic, but said they will not be intimidated by the barbarism for the militant group.
A propaganda video showing the execution of kidnapped US reporter Steven Joel Sotloff by a militant from the Islamic States (formerly ISIS) has appeared on YouTube and other video sharing sites.
The Assad regime and militants from the Islamic State (formerly ISIS) have been accused of committing “mass atrocities” in Syria, in a report by the UN Human Rights Council.