The Syrian government has sent text messages to residents and rebels in eastern Aleppo telling them to leave the area within 24 hours.
Government forces said that they were preparing a major offensive to push opposition fighters out of the besieged eastern half of the city.
"To the armed people in the neighbourhoods of east Aleppo, we are giving you 24 hours only to decide if you are leaving. Your leadership abroad is incapable of getting you out. Whoever wants to stay alive must drop his weapons and we will secure his safety. After the 24 hours is up we will implement a strategic attack using highly sophisticated weapons," the messages read.
"The opposition leadership that stays in hotels and castles enjoying a luxurious life doesn't care about the poor Syrian citizens in east Aleppo. They are using you for their personal benefit. We are giving you, the sick and the wounded, 24 hours to exit if you want."
The move comes as Russia continues to build its naval presence off the coast of Syria, and as major Russian aircraft carriers arrive off the coast.
"This could be an all-out assault in the next 24 hours," Al Jazeera's Osama Bin Javaid, reporting from Gaziantep on the Turkish-Syrian border, said.
Messages from the government have been sent to eastern Aleppo residents before, but usually in leaflets dropped from the sky, or on loudspeakers.
"This is part of the psychological warfare being waged on the besieged city," Bin Javaid reported. "Rebels say it is one of the tactics the government uses to draw them out and make them use their weapons."
Speaking on the situation inside eastern Aleppo, Bin Javaid said that the people living there are desperate.
"Residents are making fun of text messages being sent, because there is no electricity to charge their mobile phones and no way to add credit to their phones," Bin Javaid added.
More than 250,000 people are tightly packed into the besieged eastern part of Aleppo, and the United Nations has warned of potential mass starvation there.
Russian and Syrian government forces say rebels are to blame for the inability of humanitarian groups to deliver food and aid, particularly during an earlier ceasefire.
For the last two weeks, rebels have been trying to break the government siege of eastern Aleppo, but their gains were reversed after troops loyal to President Bashar al-Assad recaptured districts of western Aleppo, which is largely controlled by government forces.
Source: Al Jazeera News