The Syrian opposition on Friday denounced a "large-scale massacre" by troops and militiamen in a Sunni village in the northwest after a watchdog said at least 50 people, mostly civilians, were killed.
The Syrian National Coalition called for international action, citing witness reports of civilians being stabbed to death in Bayda, a Sunni village outside the port of Banias.
"The Coalition calls on the Arab League and the United Nations to act rapidly to save the civilians of Bayda, Banias and other villages across Syria," a statement said, accusing the regime of "war crimes and genocide."
"Several sources in the village say at least 50 people were killed in summary executions and shelling in Bayda village," a southern suburb of the Alawite-majority city, Syrian Observatory for Human Rights chief Rami Abdel Rahman told AFP on Thursday.
He was speaking after fierce clashes erupted in the area.
The official SANA news agency said troops killed "terrorists" -- the regime term for insurgents -- and seized arms in an operation targeting rebels.
An Observatory statement said some people "were summarily executed, shot to death, stabbed or set on fire."
Regular forces were supported by pro-regime "shabiha" militiamen, added the statement from the Observatory, which relies on a network of activists and medics on the ground for its information.
"Dozens of civilians from Bayda have gone missing, and we don't know whether they have been arrested, killed or fled," said Abdel Rahman.
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"Many villagers have fled to Sunni districts in southern Banias, as there is no refuge for them in Alawite areas," he added.
The Banias region is predominantly Alawite, an offshoot of Shiite Islam and the sect of President Bashar al-Assad, while the insurgents battling to topple his regime are mainly Sunni Muslims.
The region's three main coastal cities of Banias, Latakia and Tartus and their surrounding areas form the "Alawite heartland," where analysts say Assad could seek refuge if his regime falls.
"The regime will not allow the presence of combatants in this area," Abdel Rahman said, referring to rebel forces.
The Britain-based Observatory said on Friday regime forces were conducting a wave of arrests in the Sunni southern suburbs of Banias.
"Heavy gunfire has been heard, and we fear there may be a new sectarian massacre."
On Thursday, the Coalition said the soldiers and militiamen carried out "ugly crimes, including summary executions... to seek revenge... because the regime hasn't forgiven Banias and Bayda for standing alongside Daraa... at the start of the Syrian revolution."
Banias, along with Daraa in the south, the cradle of the uprising, saw some of the first demonstrations against the regime in March 2011.
The United Nations says that at least 70,000 people have been killed in the conflict that is now in its third year.