The three-year war has only intensified and witnessed its bloodiest phase just last month. Over 1,800 people were killed during a 10-day stretch in July.
It has pushed the estimated death toll in three years of war to over 170,000.
UN investigators say opposition activists are abandoning their groups in large numbers to join the Islamic State movement. The group is fighting against forces loyal to Bashar al-Assad as well as other opposition groups such as the Nusra front.
The Islamic State controls large parts of northeastern Syria and Western Iraq, including the city of Mosul.
Presenter: Hazem Sika
Joseph Kechichian, a senior writer at Gulf News.
Louay Safi, a member of the opposition and the former spokesperson for the Syrian National Council.
Peter Neumann, a director of the International Centre for Study of Radicalisation and a professor of security studies at King's College London.