Forces linked to Syria's new rulers have engaged in heavy fighting with fighters loyal to deposed President Bashar al-Assad in a coastal area of the country, BBC said in a report on its website.

It is the worst violence in Syria since rebels toppled Assad in December and installed an Islamist transitional government.

A war monitoring group, the British-based Syrian Observatory for Human Rights, said more than 70 people have been killed.

A curfew has been imposed in the port cities of Latakia and Tartous, where the fighting has broken out.

The clashes started when government forces were ambushed during a security operation in Latakia.

Reinforcements have been sent, and videos posted online show heavy gunfire in some places.

The coastal region is the heartland of the Alawite minority, and a stronghold of the Assad family, which belong to the Alawite sect.

Estimations of the number of people killed in the violence vary, and the BBC has been unable to independently verify them.

The Syrian Observatory for Human Rights said on Friday that 71 people had been killed, including 35 members of government forces, 32 gunmen affiliated to the former regime's army, and four civilians.

The clashes left tens of others injured, the human rights group said.

Gunmen, some from the former regime, had ambushed military forces, checkpoints and headquarters along the coastline, the organisation said.

Local gunmen took hold of military zones, where they holed up in areas in the Latakia mountains to launch attacks, while others holed up in Jableh city.

Members of the former regime army have been deployed in several coastal towns and villages, while military forces have been ambushed on highways.

Late on Thursday, Syrian-based Step news agency reported that government-aligned forces had killed "about 70" former regime fighters, while more than 25 others were captured in Jableh and the surrounding areas.

There have also been reports of clashes in the cities of Homs and Aleppo.

The crackle of heavy gunfire on residential streets in Homs could be heard on unverified videos on social media.

A spokesman for Syria's defence ministry, Colonel Hassan Abdul Ghani, issued a warning to Assad loyalists fighting in Latakia via state media.

"Thousands have chosen to surrender their weapons and return to their families, while some insist on fleeing and dying in defence of murderers and criminals. The choice is clear: lay down your weapons or face your inevitable fate," he said.

The region has become a major security challenge for interim president Ahmed al-Sharaa.

Alawite activists said their community had been subjected to violence and attacks since Assad fell, particularly in rural Homs and Latakia.

He is also facing resistance in the south, where there have been clashes with Druze forces in recent days.