The general command of the Syrian army said Monday that the rebels' attack a day earlier against a town in the central province of Hama killed as many as 42 people.
The al-Qaida-linked Nusra Front killed 42 people after storming the town of Ma'an on Sunday, the Syrian military said in a statement.
The rebels attacked the town in large numbers using various weapons, committing acts of arson and sabotage, said the statement, adding that the attackers forced residents out of their homes.
The military stressed that this "heinous and criminal act" will not go unpunished.
The military's general command said that the crime came at a time the Syrian government is exerting strenuous efforts to end the suffering of the Syrian people.
Meanwhile, activists said that the Nusra fighters attacked the town and killed many of the Alawite minority, an offshoot of Shiite Islam, to which the ruling elite in Syria belongs.
The attack apparently was unleashed by sectarian motives as the majority of the residents of Ma'an are Alawite.
The country's nearly three-year-old conflict has taken a sectarian turn recently with al-Qaida-linked groups and other ultra-radical groups fighting to topple the administration of Syrian President Bashar al-Assad to establish an Islamic emirate.