Opposition-controlled parts of Syria's battered northern city Aleppo came under total siege on Sunday, after government forces severed the last route out of the east.
Beleaguered rebels have failed to thwart a major Russian-backed army offensive around Aleppo city, which has been devastated by the country's five-year conflict.
On Sunday, regime fighters descended on the Castello Road and fully cut it, said Rami Abdel Rahman, head of the Britain-based Syrian Observatory for Human Rights.
"The eastern neighbourhoods are now completely besieged," he told AFP.
The army had advanced on July 7 to firing range of the key supply route but had not reached the road itself.
Aleppo city is divided roughly between government control in the west and rebel control in the east, where an estimated 300,000 civilians still live, according to the United Nations.
The Castello Road had been used by rebels but also by shopkeepers bringing in produce for residents and by villagers visiting relatives in the city.
"Aleppo is now 100% besieged," a rebel fighter from the Aleppo Revolutionaries group told AFP.
"The army has reached the road and even arrested a group of civilians who were walking there," the fighter said.
"They are now setting up sandbag barriers," he added.
AFP's correspondent in one rebel-controlled neighbourhood said at least six air strikes targeted the eastern opposition neighbourhoods after the route was severed.
On Saturday, at least 28 civilians including children were killed in bombardment of the eastern districts, according to the Observatory, which relies on a wide network of sources on the ground.
Another four people died in rebel rocket fire on the western government-controlled neighbourhoods, it said.
According to the United Nations, nearly 600,000 people are living under siege in Syria, most of them surrounded by government forces, although anti-regime groups also use the brutal tactic.
Eastern Aleppo is not yet designated by the UN as besieged, but residents have already complained of food shortages and skyrocketing prices.
Shopkeepers have begun rationing their products and there have been long queues outside bakeries.
A leading opposition group had warned last week that hundreds of thousands of civilians risked starvation if the Castello Road was cut.
Anas al-Abdeh, head of the Istanbul-based opposition National Coalition, said on Tuesday his group was "quite worried" about a possible siege.
Aleppo was once Syria's commercial powerhouse but has been ravaged by fighting since mid-2012, with several temporary truces failing to bring an end to the violence there.
More than 280,000 people have been killed and millions have been forced to flee their homes since Syria's conflict first erupted in March 2011.