Syria state media say government troops are battling insurgents inside the country's largest city Aleppo for the first time since 2016.

The Syrian military said on Saturday that rebels had entered large parts of Aleppo city during an offensive in which dozens of soldiers had been killed, forcing the army to redeploy - the biggest challenge to President Bashar al-Assad in years.

Rebel forces opposing President Bashar al-Assad have launched their biggest offensive in years this week, controlling a majority of Syria's second city of Aleppo according to a monitor.Government forces offered little resistance,