Syrian government forces have effectively cut the only road into rebel-held areas of the city of Aleppo, military sources and rebels say.
After heavy fighting and air strikes overnight, troops advanced to within 1km (0.6 miles) of the Castello Road, within range of small arms fire.
Rebels said that meant no-one could now get into or out of the east of the city, home to up to 300,000 people.
The assault came hours after the government declared a 72-hour truce.