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 monitoring group says 973 civilians have been killed in revenge attacks against the Alawite sect since Thursday.

Hundreds of people were killed in Syria over four days after violent clashes between the army and loyalists of the deposed president Bashar al-Assad swept its western coastal region.

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. Hundreds of people have been killed in the crackdown and fighting between the security forces and supporters of former President Bashar al-Assad since Thursday.

On March 6, armed fighters loyal to former Syrian president Bashar Al Assad launched an attack on Syria's interim-government troops in Latakia. Syrian authorities, supported by pro-government militias,