Syrian leader Ahmed Sharaa called for peace on Sunday after hundreds were killed in coastal areas in the worst communal violence since the fall of Bashar al-Assad.

The Syrian Observatory for Human Rights, a British-based war monitor, said on Saturday more than 1,000 people had been killed in the two days of fighting in the Mediterranean coastal region in some of the worst violence for years in a 13-year-old civil conflict.

“We have to preserve national unity and domestic peace, we can live together,” Sharaa, the interim president, said as clashes continued between forces linked to the new Islamist rulers and fighters from Assad's Alawite sect.

“Rest assured about Syria, this country has the characteristics for survival,” Sharaa said in a circulated video, speaking at a mosque in his childhood neighbourhood of Mazzah, in Damascus. “What is currently happening in Syria is within the expected challenges.”

Assad was overthrown last December after decades of dynastic rule by his family marked by severe repression and a devastating civil war.

Syrian security sources said at least 200 of their members were killed in the clashes with former army personnel owing allegiance to Assad after coordinated attacks and ambushes on their forces that were waged on Thursday.

The attacks spiralled into revenge killings when thousands of armed supporters of Syria’s new leaders from across the country descended to the coastal areas to support beleaguered forces of the new administration.

The authorities blamed summary executions of dozens of youths and deadly raids on homes in villages and towns inhabited by Syria’s once-ruling minority on unruly armed militias who came to help the security forces and have long blamed Assad’s supporters for past crimes.

Clashes continued overnight in several towns where armed groups fired on security forces and ambushed cars on highways leading to main towns in the coastal area, a Syrian security source told Reuters on Sunday.

A security source added the pro-Assad insurgents were now escalating their campaign, staging hit and run attacks on several public utilities in the last 24 hours.

They damaged a main power station that cut electricity across parts of the province, while a main water pumping station and several fuel depots were disrupted.

“They are now trying to create havoc, disrupt life and attack vital installations,” he added.

In Latakia, police mounted new checkpoints inside the city. Two residents said sounds of gunfire and artillery could be heard on the outskirts of the coastal city.

A security source said clashes continued in several areas.

The Damascus authorities were also sending reinforcements to beef up their security presence in the mountainous province, where thick forests in rugged terrain were helping the anti-government fighters, another police source said.