The Syrian city of Deir Ezzor (also spelled “Deir al-Zor”) has been a block-to-block battleground between the Islamic State and Syrian regime forces for over a year, a key strategic crossroads between the Syrian and Iraqi wings of the “caliphate.”

The fighting has grown more intense over the past few weeks, culminating in this weekend’s mass abduction of some 400 people.

According to the Syrian Observatory for Human Rights in London, a few days later, ISIS released over half of the people it abducted from Deir Ezzor. CNN reports the freed detainees included “women, children under the age of 14, and men over the age of 55.”

This came as a relief to those who feared the prisoners, including the families of fighters loyal to the Syrian regime, could be tortured or executed by the Islamic State. It is believed there were hundreds of casualties during the weekend’s fighting, denounced by the Syrian government as a “horrific massacre against the residents.”

The UK Mirror quoted a Syrian government source who said some of these deaths were deliberate executions and beheadings, rather than collateral damage from the fighting.

CNN noted that it could not independently confirm the Observatory’s report. Reuters relayed the same information from the Observatory, along with the news that the male prisoners were retained by ISIS for questioning. In fact, another 50 men were reportedly taken captive during raids on Tuesday.

A spokesman for the U.S. State Department demanded “the immediate and unconditional release of any civilians who were taken captive and of all those held by ISIL,” condemning violence against civilians in the besieged city.