Syrian government and opposition delegates said talks to end their country’s civil war have reached an impasse, with the United States and Russia backing the rival camps and trading accusations over the deadlock.

Around 300 more people have been evacuated from besieged rebel-held neighbourhoods of Syria’s third-largest city, Homs, a Syrian Red Crescent official said.

Syrian warplanes and artillery have pounded the central city of Homs, subjecting the former rebel stronghold to its worst bombardment in months, activists said.