Syrian security forces are alleged to have killed hundreds of civilians belonging to the Alawite minority group in continuing violence along the countrys coast, according to a war monitoring group.
The British-based Syrian Observatory for Human Rights (SOHR) said some 745 civilians had been killed in around 30 "massacres" targeting Alawites on Friday and Saturday.
BBC News has not been able to independently verify these claims.
Hundreds of people have reportedly fled their homes in the region - a heartland of deposed president Bashar al-Assad, who also belongs to the Alawite sect.
A total of more than 1,000 people have been killed in the past two days, the SOHR said, in what is the worst violence in Syria since rebels toppled the Assad regime in December.
This figure includes dozens of government troops and gunmen loyal to Assad, who have been locked in clashes in the coastal Latakia and Tartous provinces since Thursday.
Some 125 members of the Islamist-led government security forces and 148 pro-Assad fighters have been killed in the violence, according to the SOHRs report.
A Syrian defence ministry spokesman told the countrys Sana news agency that the government had re-established control after "treacherous attacks" against its security personnel.
The violence has left the Alawite community in "a state of horror", an activist in the city told the BBC on Friday, with hundreds of people reportedly fleeing affected areas.
Large crowds sought refuge at a Russian military base at Hmeimim in Latakia, according to the Reuters news agency.
Video footage shared by Reuters showed dozens of people chanting "people want Russian protection" outside the base.
Meanwhile, dozens of families have fled to neighbouring Lebanon, according to local media.
The UNs special envoy for Syria, Geir Pedersen, said he was "deeply alarmed" by "very troubling reports of civilian casualties" in Syrias coastal areas.
He called on all sides to refrain from actions which could "destabilise" the country and jeopardise a "credible and inclusive political transition".
Alawites, whose sect is an offshoot of Shia Islam, make up around 10% of Syrias population, which is majority Sunni Muslim.