According to Press TV, following its Saturday attack on Dayr al-Zawr, ISIL "abducted at least 400 civilians from the residents of the al-Baghaliyeh neighborhood it captured, and adjacent areas in the northwest of the city," the so-called Syrian Observatory for Human Rights (SOHR) said on Sunday.
Rami Abdel Rahman, the SOHR director, added that all of the abductees were Sunni Muslims, including families of pro-government fighters. He added that they were transported to other areas under ISIL control.
"There is genuine fear for their lives, there is a fear that the group might execute them as it has done before in other areas," he stated.
Syria's state news agency SANA said some 300 civilians were killed in the Daesh attack on the city.
Syrian Prime Minister Wael al-Halqi condemned the "barbaric massacre," saying the responsibility for the crimes lies with the supporters of terrorist groups active the Arab state.
Dayr al-Zawr has been effectively under siege by Daesh terrorists since early 2015, when the militants launched an offensive, capturing the city of Palmyra in Homs Province, then cutting off the remaining supply line to the city.
The Daesh siege has led to a severe food crisis in Dayr al-Zawr, where 70 percent of the residents are women and children.