By local counts more than 150 people have been killed by intense shelling, rocket attacks and air strikes on Eastern Ghouta since overnight on Monday.
The Syrian Observatory for Human Rights said the death toll had risen to 250 in just 48 hours.
Many bodies are still trapped under rubble. Overwhelmed first responders are struggling to keep up with the demands of the injured, let alone take care of the dead.
At least two health workers have been killed in the assault, according to the Union of Medical and Relief Organisations (UOSSM), which runs hospitals in opposition-held Syria, as well as one White Helmets volunteer who was responding to a bombing.
Pictures and video too graphic to publish sent to The Independent by residents and activists show bodies grey with dust save for streaks of red blood down their faces and clothes.
On Tuesday, resident Wassim Khatib said he feared the death toll would be even worse than the previous day as three war planes droned overhead and the booms of strikes could be heard in the background.
“I can’t think straight. People are so afraid,” he said.
Hundreds of people have been injured and at least seven medical facilities hit by air strikes as Syrian President Bashar al-Assad and his Russian allies step up the onslaught ahead of what is anticipated to be a final ground assault to crush the rebel enclave once and for all.
Many families are taking shelter in basements and makeshift tunnels underground in the districts of Old Damascus, Bab Touma, Abu Rummaneh which were once used to smuggle in fuel, medicine and machinery.
Ghouta is one of four supposed de-escalation zones created in a May 2017 agreement brokered by Russia, Turkey and Iran to quell fighting between rebel forces and the regime – but the recent violence there been some of the most brutal of Syria’s civil war, now entering its eighth year.
The Damascus suburb has been besieged by government forces for years and was also the scene of a sarin and chlorine gas attack in 2013, one of the worst chemical incidents in modern history.
Rebel infighting is rife, and the Syrian government says it controlled by factions allied to extremists groups such as al Qaeda.
In recent months, however, Mr Assad’s government has tightened the siege, leaving its 400,000 civilians struggling with dwindling food and medical supplies. At the same time, it has stepped up the military campaign.
The tactics echo several other battles in Syria's war, including Homs, Daraya and Aleppo.
“Russia is supposed to be a guarantor, but instead it is propping up this violence, saying it is killing terrorists,” Bassma Kodmani, a senior negotiator from the opposition Syrian Negotiation Commission, told The Independent.
“Killing 100 civilians for one terrorist is a terrible strategy.
“We Syrians see and share all these pictures of death, but I don’t know if the scale of the horror is obvious to other people.
“After seven years of war I think maybe this is the most terrible aspect of it all, the fatigue. Since [the fall of Aleppo in December 2016] it has been hard to convey that the rest of Syria is still suffering.”
On Tuesday the UN’s Children’s Fund expressed its outrage at the violence by releasing a blank statement, arguing “no words will do justice to the children killed, their mothers, their fathers and their loved ones.”
The message from Unicef’s regional director Geert Cappelaere contained ten empty lines with quotation marks to indicate the missing text before finishing with a footnote.
“We no longer have the words to describe children’s suffering and our outrage,” it said.
“Do those inflicting the suffering still have words to justify their barbaric acts?”
UN officials have repeatedly called for a immediate cessation of hostilities in Ghouta and the resumption of aid shipments.
The fall of the eastern rebel-held side of Aleppo at the end of 2016 marked a turning point in Syria’s conflict, shifting the tide of the war in President Assad’s favour.
After more than seven years of fighting which has left half a million people dead and caused half of the pre-war population of 18 million to flee their homes, however, the war is far from over.
“The UN tells them to stop, and what? Nothing,” said Mr Khatib. “And more people die every minute.”
Join our new commenting forum
Join thought-provoking conversations, follow other Independent readers and see their replies