Syria's new authorities under interim President Ahmed al-Sharaa have sought to disband armed groups
The Syrian Observatory for Human Rights war monitor has reported that 745 Alawite civilians were killed in Latakia and Tartus provinces.
Syrian authorities said the violence began when remnants loyal to Assad launched a deadly and well-planned attack on their forces on Thursday.
There were no immediate claim of responsibility for the attack.
Sharaa was appointed Wednesday to lead Syria for an unspecified transitional period
No group has claimed the four activists' abduction and they have not been heard from since.
Ankara-backed rebels played a key role in supporting Sharaa's Islamist group Hayat Tahrir al-Sham (HTS), which headed a rebel alliance that seized Damascus on December 8, toppling longtime ruler Bashar al-Assad.
The seismic change in Syria is expected to yield deeper Turkish sway just as a change of US administration is raising questions over how long Washington will keep backing the country's Kurdish-led forces.
Assad fled Syria following a lightning offensive spearheaded by the Islamist Hayat Tahrir al-Sham (HTS), more than 13 years after his crackdown on democracy protests precipitated one of the deadliest wars of the century.
Nato has ruled out sending ground troops to fight against Islamic State militants in Syria, Nato General Secretary Jens Stoltenberg told a Swiss newspaper, stressing the need to bolster local forces in the conflict.
An air strike believed to have been carried out by the US-led coalition killed four Syrian military personnel in Deir al Zor province, which is mostly held by Islamic State, a monitoring group says, in what would be the first time coalition warplanes had hit Syrian government forces.
RAF jets have carried out their second set of air strikes in Syria since MPs backed military action against so-called Islamic State in the country.
The mass shooting in California is being investigated as "an act of terrorism," the FBI said, amid reports the female assailant had pledged allegiance to the Islamic State group on Facebook.
Thai police say they were warned by Moscow that 10 Syrians working for the so-called Islamic State (IS) entered Thailand in October to target Russians.
The UK has started bombing targets of the so-called Islamic State (IS) in Syria, and a number of Syrians have been giving their reaction to the British decision.
A video released online by Islamic State purportedly showed the beheading of a man the group said was a Russian spy its fighters had captured and who had been in Syria and Iraq since last year, the SITE monitoring group reported.
RAF Tornado jets have carried out their first air strikes against so-called Islamic State in Syria, the Ministry of Defence has confirms. The strikes come hours after MPs voted in favour of UK air strikes in Syria.
Scottish MPs will take part in the Commons debate and vote later on whether the UK should launch air strikes against so called Islamic State targets in Syria.
The PM is to ask his cabinet to endorse a one-day Commons debate and vote on Wednesday over UK air strikes against so-called Islamic State in Syria.
