The death toll from two days of clashes between security forces and loyalists of ousted Syrian president Bashar al-Assad and revenge killings that followed has risen to more than 1,000, including nearly 750 civilians,

The clashes, which erupted on Thursday, marked a major escalation in the challenge to the new government in Damascus.

A war monitoring group said on Saturday that the violence was one of the deadliest incidents since Syria's conflict began 14 years ago.