Rebels fighting troops loyal to Syria's President Bashar al-Assad clashed with the army Monday as they pushed an advance into the coastal province of Latakia, a monitoring group said.
The clashes in the western province come a day after rebels seized five majority Alawite villages in the area, said the Syrian Observatory for Human Rights.
By Monday, however, the army had retaken one village, Beit al-Shakuhi, the group said.
Syria's uprising is Sunni-dominated, like the country's population, while Latakia and neighbouring Tartus are home to members of Assad's Alawite minority community.
The fighting in the province over the past two days has been fierce, said Observatory director Rami Abdel Rahman.
"At least 20 rebels have been killed, as have 32 army and pro-regime militia troops," he told AFP.
"The army and pro-regime militia from the National Defence Force and the Baath battalions are sending reinforcements to push the rebels back," he added.
The fighting is concentrated near the mountainous Jabal al-Akrad area in northern Latakia, and rebels are also trying to advance in Jabal Turkman.
These areas are home to a mixed population of Sunnis and Alawites, "making it practically impossible to avoid the conflict there from turning sectarian", Abdel Rahman warned.
The Alawite sect is an offshoot of Shia Islam, and Assad hails from the Latakia town of Qardaha.
An anti-regime activist in Latakia said the rebels decided to open a new front in the coastal province because pockets already under their control were being shelled from nearby villages.
"There is a battle to liberate the areas that are being used as launching pads to shell civilians" in villages out of army control, Omar al-Jeblawi told AFP via the Internet.
"Morale is very, very high," he said, adding that the developments on Syria's coast "are significant not just for our area, but for the whole of Syria."
Jeblawi said several anti-regime battalions are taking part in the fighting, including mainstream, local rebel groups and jihadists.
But other activists, such as Latakia-based Sema Nassar, were opposed to opening up the front at this time.
The rebels "have a habit of escalating without preparing as soon as they feel they have enough weapons. But they are not ready... and the regime's response will be crazy."
Nassar said the rebels have taken prisoner an Alawite cleric, Badr Ghazal, from the village of Baruda after he issued a religious decree urging rebel forces "stamped out completely."
For its part, the main opposition National Coalition praised the rebel escalation.
"The Syrian Coalition applauds Free Syrian Army fighters on the Syrian coast," said the group.
Despite pockets of resistance to Assad's regime in Latakia, most of the province is still firmly under army control.