The Syrian army says that pro-government forces have cut off all supply routes into the eastern, rebel-held part of Aleppo in the country's north.
According to the UK-based Syrian Observatory for Human Rights, eastern Aleppo has been under effective siege since July 11, and advances in recent days by forces loyal to President Bashar al-Assad have strengthened their control of the only route in.
"Today there is no way at all to bring anything into Aleppo," Observatory Director Rami Abdel Rahman said on Wednesday.
Once Syria's largest city, Aleppo has been roughly divided between government control in the west and rebel control in the east since mid-2012.
Taking full control of the city would be a significant victory for Assad.
An advance by pro-government forces around the only remaining supply route into the eastern sector this month enabled them to fire on it at close range, making the battlefront Castello road too deadly to use and putting at least 250,000 people in rebel-held districts under siege.
"We're hearing from activists and witnesses that regime forces are taking more and more of that area," said Al Jazeera's Mohammed Jamjoom, reporting from Gaziantep on the Turkish side of the Syria-Turkey border.
"That is posing a real precarious problem for rebel fighters because the city is being increasingly encircled by regime forces."