The Syrian Observatory for Human Rights monitoring group said that fighters with Islamist groups such as Jund Al Aqsa were behind the deaths in Maan village on Sunday.
Observatory director Rami Abdel Rahman told Agence France Presse that there were no immediate details available on how the civilians had been killed, but he said that 10 of the slain appeared to come from a single family.
The group said at least 20 members of the National Defense Forces, a pro-regime militant organization, had also been killed in the attack, according to AFP.
A video posted by Jund Al Aqsa on YouTube called "the liberation of Maan village"  reportedly shows forces moving into the area, opening fire on the village and raising a black flag often associated with radical jihadist groups, AFP reported.
There is no footage in the YouTube clip of the reported civilian deaths.
Syria's President Bashar Assad is a member of the Alawite minority, whose belief is a branch of Shiite Islam. 
The uprising against Assad is largely comprised of Sunni Muslims and has been recently populated by extremist groups, who consider non-Sunni Muslims to be infidels, according to AFP.