SIS militants reportedly abducted at least 230 people including 60 Syrian Christians after they took control of the town of al Quaryatayn in Homs province, according to the Syrian Observatory for Human Rights (SOHR).
Many children and women are among the Christians held hostage, according to the UK-based observatory.
The town of al Quaryatayn was captured overnight by ISIS after they were involved in heavy clashes against Syrian troops, which involved a number of suicide bombing assaults on several military checkpoints.
The town, which is the biggest capture by ISIS militants in Syria since the capture of Palmyra in May, is located in a strategic position near a road that connects the ancient city directly to the Qalamoun Mountains, along the border with Lebanon.
The insurgency is known to commit mass punishments against those who do not comply with their restrictions and regulations, including members of religious minorities and Sunni Muslims.
The fate of many of these abducted Syrian civilians is unknown, including a number of priests who went missing and are suspected to be held by the militant group, according to Christian groups