The military, associated with Syria’s new rulers, is engaged in a fierce battle with fighters loyal to President Bashar al-Assad, abdicated in the country’s coastal regions, the BBC said in a report on its website.
It is Syria’s worst violence as rebels overthrew Assad in December and established an Islamist transitional government.
The War Watch Group, a UK-based Syrian Human Rights Observatory, said more than 70 people had been killed.
Port cities in Latakia and Tartas are subject to curfews that have led to combat.
The clash began when government forces were ambushed during a security operation in Latakia.
Reinforcements have been sent, and videos posted online show fierce gunfires in several locations.
The coastal region is the center of the Alawite minority and is the base of the Assad family, a member of the Alawite faction.
Estimates of the number of people killed in violence were varied and the BBC was unable to independently verify them.
The Syrian Human Rights Observatory said Friday that 71 people were killed, including 35 members of the government forces, 32 gunmen from the former government forces, and four civilians.
Human rights groups said other people were injured in the clash.
The organisation says gunmen from previous administrations were ambushing troops, checkpoints and headquarters along the coastline.
Local gunmen embraced the military zone, where they opened a hole in the area of Mount Latakia, but others drilled a hole in Jable City.
Members of the former administration’s army are deployed in several coastal towns and villages, but the troops are ambushed on the highways.
Late Thursday, Syria-based Step News Agency reported that troops alongside the government killed “about 70” former regime fighter jets, but more than 25 people were captured in Jableh and surrounding areas.
There have also been reports of conflicts in the cities of Homs and Aleppo.
The crackling of fierce gunshots in a residential area of Homs could be heard in unverified social media videos.
Colonel Hassan Abdul Ghani, a spokesman for Syrian Ministry of Defense, has issued a warning to Assad Loyalists fighting in Latakia via state media.
“Thousands have chosen to abandon their weapons and return to their families, but some insist on escaping and dying in the defense of murderers and criminals. The choice is clear: put your weapon or face an inevitable fate.”
The region has been a major security challenge for interim president Ahmed al-Sharaa.
Alawian activists said their communities had been exposed to violence and attacks since Assad collapsed, especially in rural Homs and Latakia.
He also faces resistance in the South. There was a recent clash with the Druze army.