Aid has been locked out from rebel-held areas of Aleppo for the longest period since the Syrian civil war began due to an escalation in air strikes and bombardments, driving up food prices and hampering efforts to ease the plight of residents.

“For the last few weeks we have not been able to bring supplies into (Aleppo) city itself,” said Christy Delafield, senior communications officer for Mercy Corps, which runs the largest non-governmental aid operation inside Syria.

Delafield told Reuters in a phone interview from Turkey that hourly shelling has stopped aid delivery for a long time now.

Aleppo, Syria’s largest city before the civil war with a population of more than two million people has been divided for years into rebel and government sectors. Capturing Aleppo is one of President Bashar al-Assad’s key strategic objectives. Assad said in a speech that Aleppo would be a “graveyard” for the ambitions of his regional foe, Turkish President Tayyip Erdogan, who has backed rebel groups.

The opposition-held part of Aleppo has been cut off from the outside world by the escalation in air and artillery strikes on the only road in, putting hundreds of thousands of people under effective siege.

Between 200,000 and 300,000 people are still thought to live in the rebel sector, the Syrian Observatory said, in harsh conditions made worse by the latest attempt to besiege them by cutting off the Castello Road, named after Aleppo’s old castle. The route has been dubbed the “Road of death”.

The road had long been under sniper fire, but attacks from the air and artillery sharply increased less than two weeks ago, with more planes flying and new rockets and guns moved into range.

The international focus in Syria in recent weeks has partly turned towards the conflict with ISIS fighters, as both the government and its enemies have made gains at the expense of the ultra-hardline Islamist militants on several fronts.

But the separate hope of foreign powers — that the wider civil war could also be resolved — has broken down, with Aleppo potentially the biggest battlefield of all. Hundreds of people have been killed there since peace talks broke off.

Mercy Corps, which reaches about 570,000 people monthly in Syria and more than 75,000 people in Aleppo city, has been distributing flour to bakeries and food parcels to families which rely on them for sustenance.

As aid stocks run down in Aleppo, food prices in markets have risen, putting extra strain on the limited finances of people weakened by more than five years of civil war.

“Any time we are unable to access the city we have seen a corresponding increase in prices in markets,” Delafield said, adding that they have already seen less diversity in available food and price rises in some, but not all, staples.

On Tuesday, the price of one kg of sugar had risen 63 percent to 425 Syrian pounds ($0.90) from 260 Syrian pounds ($0.55) in February.

One kg of potatoes had risen almost 70 percent to 135 Syrian pounds from 80 Syrian pounds in mid-May, and a can of beans had risen 50 percent to 150 Syrian pounds from 100 Syrian pounds in mid-May.

Aleppo has been at the center of a military escalation which saw Geneva peace talks break down in April when the main opposition alliance withdrew over what it described as a worsening situation on the ground.

Humanitarian workers complain that a lack of safe access is limiting work in rebel-held areas of Aleppo and the surrounding countryside. Two Aleppo medical facilities supported by international medical charity Medecins Sans Frontieres (MSF) were hit by air strikes in the past two weeks.

“The world is turning a blind eye to the carnage in Aleppo,” said Muskilda Zancada this week, MSF’s Syria head of mission.

International humanitarian law prohibits targeting of civilian infrastructure in war, but the frequency with which hospitals, schools and other places where civilians gather such as markets are being hit in Syria is causing despair among humanitarian workers and residents.

The Syrian government and their Russian allies have repeatedly denied their air strikes deliberately target civilian infrastructure such as hospitals.