The warning came via text message, urging the sick and wounded to flee before a “strategically planned assault using high precision weapons occurs within 24 hours.”
Rebels were also given an ultimatum to lay down their arms and renounce their leadership, or be killed.
The message was likely sent by the Syrian government as the regime is likely the only party capable of sending a mass text to the entire population.
While there were no reports of a bombardment by Monday afternoon, witnesses told CNN that fighter jets had been spotted in the city, as deadly skirmishes were reported all over Aleppo.
Russian warplanes have since September last year backed the regime with airstrikes over rebel-held positions, pounding eastern Aleppo, where schools and hospitals have been crushed.
The text message warning is seen as a response to Syrian rebels launching an offensive
last month to break the regime’s siege on eastern Aleppo.