A war monitoring group said more than 1,000 were killed in revenge attacks and clashes between Syrian security forces and loyalists of ousted President Bashar Assad.

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

The killings occurred in the heartland of Syria’s Alawite minority, escalating after a nascent insurgency formed against the Sunni Islamist government.

The violence that has killed hundreds across Syria reached Damascus and Aleppo on Monday, after Ahmed al-Sharaa vowed to bring those responsible to justice.

At least 973 civilians, including women and children, have been killed in Syria in recent days as forces of the new administration seek to crush loyalists of former President Bashar al-Assad, according to the Syrian Observatory for Human Rights (SOHR).

A Syrian security source said the pace of fighting had slowed around Latakia, Jabla and Baniyas, while forces searched surrounding mountainous areas where an estimated 5,000 pro-Assad insurgents were hiding.

An eruption of violence in Syria over the weekend has led to global calls for peace as the nation sees its deadliest weekend since the fall of the Assad regime in December.

Syria’s interim President Ahmed Al-Sharaa has formed a committee to investigate the violence in some cities that killed hundreds of civilians in recent days and sparked condemnation from the international community.