Jihadis and their Turkish-backed allies breached Syria's second city of Aleppo on Friday, as they pressed a lightning offensive against forces of the Iranian- and Russian-backed government.

The fighters took control of "half of the city of Aleppo" as regime forces withdrew, according to the Syrian Observatory for Human Rights.

The offensive began on Wednesday, the same day that a fragile ceasefire took effect in neighboring Lebanon between Israel and Iran-backed militant group Hezbollah.