A resident in the area said that the gunmen randomly opened fire on a street as Christians were celebrating a feast day. He spoke on condition of anonymity for fear of reprisals.
The state-run SANA news agency described the attack as a "massacre" and said women and children were among the dead. But activists said that many of those killed were pro-government militiamen manning checkpoints.
The Britain-based Syrian Observatory for Human Rights said that nine of those killed were Christians. It said rebels attacked checkpoints manned by the pro-government National Defense Forces militia, killing five of them. It said the other six were civilians, including two women.
Many rebels, who are mostly Sunnis, consider Christians to be supporters of President Bashar Assad's regime. The regime is dominated by members of Assad's minority Alawite sect, an offshoot of Shiite Islam, and members of some other religious minorities consider it a bulwark against extremists among the country's Sunni majority.
SANA said the attack occurred after midnight on a road linking the Christian villages of Ein al-Ajouz and Nasrah in Homs province.
Attacks against Christians have not been uncommon in Syria since the country's crisis began more than two years ago. Two bishops were abducted in rebel-held areas in April and an Italian Jesuit priest, Father Paolo Dall'Oglio, went missing last month while on a trip to the rebel-held northeastern city of Raqqa.
