ISIS has briefly overrun a hospital complex in the eastern Syrian city of Deir al-Zour, reports say.
Activists say about 35 pro-government fighters were killed and some medical staff taken hostage. More than 20 ISIS fighters were also reported killed.
The attack was centered on al-Assad hospital, to the west of the city.
ISIS controls more than of half of Deir al-Zour and is seeking to capture the entire city.
The jihadist group has been besieging government-held areas there for two years, trapping about 200,000 civilians.
ISIS’s Amaq news agency said its fighters had carried out a “major offensive” in Deir al-Zour on May 14, storming the hospital and cutting the route between a Syrian army base and the city’s airport.
Amaq said it had also taken over a fire station, university accommodation, grain silos and territory near the al-Tayyam oil fields.
According to the Syrian Observatory for Human Rights, government forces retook the hospital after several hours of fierce fighting.
Deir al-Zour is in an oil-rich area and on a vital supply route to the ISIS stronghold of Raqqa.