BEIRUT — Progovernment forces defeated the Islamic State in its last major stronghold in Syria, state media and a monitoring group reported on Sunday, leaving the militants to defend just strips of desert territory in the country and a besieged pocket outside the capital, Damascus.

Also Sunday, more than two dozen civilians were killed as government forces and rebels traded fire across fronts in Damascus and Homs, Syria’s third largest city.

The intensified violence is testing an accord by Russia, Turkey, and Iran to suppress fighting in Syria ahead of the resumption of political talks in Geneva between the government and opposition, set for Nov. 28.

Eight civilians were killed in rebel shelling on Homs, which also put the city’s al-Walid flour mill out of service, Syria’s SANA media organization reported. It added that another two were killed by shelling or rocket fire on Damascus.

At least 17 civilians were killed in government shelling and airstrikes on the Eastern Ghouta suburbs of Damascus, which remain under opposition control, according to the Britain-based Syrian Observatory for Human Rights monitoring group.

The Civil Defense search-and-rescue group, more popularly known as the White Helmets, said one of its volunteers was killed in the line of duty.

Residents in the Ghouta region have suffered under an immense government bombardment since rebels tried to storm a military position nearby Tuesday. At least 77 civilians have been killed, according to the Observatory.

Associated Press