The international community is demanding UN access to the site of an alleged chemical attack in Syria.
Military and logistic support from Turkey was the key factor in extremists' takeover of Idlib, Syrian President Bashar al-Assad has said. He has also blamed Ankara for the failure of a UN ceasefire plan in Aleppo.
A video released by "Islamic State" purportedly shows the executions of some 30 Ethiopian Christians, who were captured by the group in Libya. The jihadists recently gained a foothold in the conflict-marred country.
'Islamic State' has taken control of large parts of a Palestinian refugee camp, Yarmouk, to the south of Damascus. Meanwhile, neighboring Jordan has temporarily closed its Syrian border amid clashes.
Syrian President Bashar al-Assad has said any talks with the United States would have to be based on mutual respect. Some 440,000 people in Syria are living under siege conditions, according to the UN.