Some 300 meters to the last remaining road in rebel hands and a further 1 kilometer to surround them completely
The Syrian army may have experienced a debacle on its march into Raqqa province and has been hard-pressed in Southern Aleppo, but throughout all that it has continued to slowly but surely take ground where it matters most -- on the northern outskirts of divided Aleppo city.
From the positions to the north of the city forces loyal to Damascus have been steadily pushing down south with the aim of linking up with the loyal western half of Aleppo which would cut off the rebels in eastern Aleppo from their last remaining link to the outside world.
The Syrian pro-government forces are at moment parked just some 250-400 meters from the last remaining road ("Castello road") leading into rebel-held Aleppo. So close in fact they can freely fire upon on the road:
— Ivan Sidorenko (@IvanSidorenko1)July 8, 2016
Syrian loyalist positions in the city itself are still a fair bit to the south, but to isolate the rebels the Syrian army doesn't have to actually reach those -- it is enough for it to reach the Sheik Mansour district (yellow enclave on the map) which is Kurdish held. In and around Aleppo the government and the Kurds are in a tactical alliance and united against the largely Islamist rebels.
Should the government forces reach Castello road the distance from there on to Sheik Mansour is just about 1 kilometer.
Obviously this is a major crisis for the rebels who have responded by unleashing all power of its improvised artillery against government-held deastern Aleppo.
Pro-government media is reporting 29 civilians have been killed with hundreds wounded as a result.
— H e b a (@HKX07)July 8, 2016
There are numerous rebel-held enclaves in Syria that are completely surrounded by pro-government forces (as well as a few pro-government enclaves surrounded by rebels, Kurds or ISIS) that have nonetheless been able to survive. This means that even if Syrian army completes the cauldron a quick victory in Aleppo is unlikely.
Nonetheless if the Syrian army completes the encirclement and is able maintain it this will have major strategic implications thus the manic and desperate strike by the rebels against civilians in government-held districts.