Syrian rebels opposed to President Bashar al-Assad said on Friday they had reached the heart of the northern city of Aleppo, after a surprise sweep through government-held towns and nearly a decade after having been forced out of the city.

A rebel commander said a fall in Iran-backed manpower created an opening this week's assault. Iran's ally Hezbollah has suffered big losses to Israel.

BEIRUT—Syria’s antigovernment rebels claimed a stunning advance into Aleppo, a major symbolic and strategic prize, in a setback for the government in Damascus and its allies Russia and Iran.Islamist-led insurgents poured into Aleppo two days after launching a stunning strike from the country’s rebel-held northwest and eight years after the city fell to forces loyal to the government of Bashar al-Assad at the end of a long siege.