Forces loyal to Syrian President Bashar al-Assad clashed with Islamic State fighters in the eastern city of Deir al-Zor on Tuesday. IS, which controls of most of the province, has laid siege since last March to remaining government-held areas in the city of Deir al-Zor.
Deir al-Zor is a strategic location. The province links Islamic State's de facto capital in Raqqa with its fighters in Iraq. Meanwhile, the Syrian government maintains a stronghold at a military airport and parts of the city.
Tuesday's fighting came as the Islamist militants released 270 of an estimated 400 civilians, most of them women and children, kidnapped over the weekend when its fighters attacked Syrian government-held areas in the town, according to The monitoring group Syrian Observatory for Human Rights.
But the released civilians will remain in Islamic State-held villages in the province.
The monitoring group also said that IS rounded up another 50 men, also on Tuesday, during raids on houses in areas seized during four days of fighting in Deir al-Zor.
Male prisoners between the ages of 14 and 55 have reportedly been held for more questioning.
Dozens were also killed in the weekend raid on government held-areas, according to the monitoring group.
A source close to the Syrian government side put the figure much higher, saying the Islamic State fighters killed at least 250 people, including pro-government fighters and their families when they attacked the neighbourhoods of Begayliya and Ayash in the city.