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.

Fearing for their lives, Syrian men, women and children waded through a river to safety in Lebanon on Tuesday, among hundreds of people who have fled to the neighbouring country to escape sectarian killing targeting their Alawite community.

Entire families including women and children were killed in Syria's coastal region as part of a series of sectarian killings by the army against an insurgency by Bashar al-Assad loyalists, the U.N human rights office said on Tuesday.

The UN human rights office has verified the killing of 111 civilians in the coastal region, but says the actual figure is far higher.