On Saturday, the Syrian news agency SANA reported that the terrorist group had massacred around 300 people in the village of al-Bagilya to the west of Deir ez-Zor.
"After their attack on Deir ez-Zor (on Saturday), IS (Daesh) abducted at least 400 civilians from the residents of the al-Bagilya suburb it captured and adjacent areas in the northwest of the city," the UK-based Syrian Observatory for Human Rights said on Sunday.
"Those abducted, all of whom are Sunnis, include women, children and family members of pro-regime fighters."
"The Observatory was informed by several reliable sources that among the 135 who were killed and executed, there are at least 50 members from the regime forces and militiamen loyal to them were killed and executed during the 'Islamic State' attack on al-Bagilya area."
Local residents told Sputnik on Saturday that around 280 people were murdered in the massacre.
"The horrific massacre carried out today by ISIL militants in al-Bagilya in Deir ez-Zor; 280 victims, including women, children and old people. Reason — cooperation with the Syrian Army," said one resident.