A car bomb has exploded in the Syrian city of Deir el-Zour, according to the Syrian state news agency.
Saturday’s explosion killed dozens of people, according to both the news agency, SANA, and to the Syrian Observatory for Human Rights.
The exact death toll is not yet clear.
The attack targeted refugees from the violence who had gathered on the east side of the Euphrates River, according to both SANA and the human rights organization.
Deir el-Zour is the center of Syria’s oil production and a regional hub for commerce.
The city is one of two in which Syrian troops declared victory over IS on Friday. The victory along the Iraqi-Syrian border followed raids by forces on either side of the border near the Euphrates Valley.
The jihadist group’s self-proclaimed “caliphate” was in tatters after it lost its urban strongholds in Syria and Iraq, with the simultaneous assaults on Deir el-Zour in Syria and Al-Qaim in Iraq, leaving IS in control of little more than small plots of territory scattered along the border.