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.
At least 25 members of Syria's al-Qaeda affiliate, al-Nusra Front, including a leader, are killed in a blast at a mosque in north-western Idlib province, activists say.
A senior member of the Islamic State (IS) group has been killed in an American drone strike in Syria last month, according to the US military.
A Bangladeshi family of 12 from England, including a baby and two grandparents, could have travelled to Syria after going missing, police have said.
A senior US commander in Afghanistan says that fighters allied with Islamic State are in contact with militants' Syrian headquarters.
The UN's cultural agency says destruction of antiquities and heritage sites in conflict zones by Islamic State and other extremist groups could amount to war crimes.
Twelve people are killed and 70 wounded in a car bomb blast and attacks by Islamic State militants in the Syrian Kurdish town of Kobani, hospital officials in the town tell Reuters by telephone.
A global survey of 40 countries finds that large numbers of people have a favourable opinion of the United States, its economy and the US-led fight against the Islamic State.
US says an air strike in Iraq has killed an Islamic State (IS) militant linked to an attack on a US diplomatic compound in Libya 3 years ago.
Tweets and YouTube videos by fighters from the Islamic State group have allowed analysts to pinpoint their movements in Iraq and Syria, highlighting the group's increasing push towards government strongholds.
Syrian Kurdish fighters say they have taken control of the Islamic State-held town of Tal Abyad, cutting off a major supply route for the jihadist group.
