Syria's Islamist-led government on Monday said it had completed a military operation against a nascent insurgency by Bashar al-Assad loyalists, as it faced Western demands for accountability over the reported killing of hundreds of civilians.

The commander of a Kurdish-led force in Syria said on Sunday the country's interim president must hold the perpetrators of communal violence in Syria's coastal areas to account, accusing Turkey-backed factions of being primarily behind the killings.

Syria's new leader has vowed accountability and an investigation after reports of mass killings of Alawite civilians triggered an international backlash against the worst violence since Bashar al-Assad's overthrow.