Armed groups killed entire families, including women and children, during an outbreak of sectarian violence in Syria last week, the United Nations human rights office said on Tuesday.

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 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.

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

A Syrian military operation against remnants of the former Assad regime has now ended, having sparked some of the worst violence seen in the country in years.

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.

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.