Almost 600 Turkish troops pushed deep into Syria early Sunday in an unprecedented incursion, evacuating Turkish soldiers guarding a historic tomb who had been stranded in territory controlled by Islamic State jihadists.
A Syrian opposition leader called on world leaders to take "immediate action" to end government attacks on rebel-held suburbs of Damascus, amid reports that some 150 people have been killed in government airstrikes in the past 10 days.
Syria said on Tuesday that US Secretary of State John Kerry had told the Damascus government in a letter delivered by Iraq that the United States and its allies were going to attack Islamic State in Syria, hours before the air strikes took place.
Al Qaeda-linked jihadists struck back against rival rebels in eastern and northern Syria on Friday after a week of internecine fighting among opponents of President Bashar al-Assad in which 500 people have been killed, a monitoring group said.
Russian officials told visiting US Under Secretary of State Wendy Sherman on Friday that Moscow would continue backing Syrian President Bashar al-Assad`s campaign against rebel forces despite peace talks due later this month.
Syria won foreign praise on Monday for starting to destroy its chemical arsenal, although an opposition activist said the world was merely giving President Bashar al-Assad time to kill more people with conventional weapons.
Al Qaeda militants battled fighters linked to the Western-backed opposition along with Kurdish gunmen in Syrian towns along the Turkish border on Friday, in clashes that killed at least 19 people, activists said.