Dozens of people were killed after Daesh launched its biggest attack in months on the Syrian regime-held city of Deir Ezzor on Saturday, said the Syrian Observatory for Human Rights.
The Observatory said at least six large explosions targeted the city and the Daesh terrorists clashed with regime forces.
Syrian regime fighter jets hit back against Daesh positions, repelling attacks along several front lines.
Daesh controls most of Deir Ezzor province, which borders Iraq, including more than half the city, and has besieged the remaining regime-held areas of the city for nearly two years.
Suspected regime air strikes hit Idlib
Meanwhile, at least eleven people were killed in air strikes on Saturday in the country's opposition-held northern Idlib province.
Dozens of others were wounded in the series of strikes. A local market is believed to have been among the targets.
The Observatory said the regime was behind the attacks.
The violence comes despite a ceasefire brokered by Russia and Turkey.
TRT World 's Abubakr Al Shamahi has more on the latest fighting in Syria.