Beirut: Medical supplies were running out in the besieged rebel-held sector of Aleppo, with victims pouring into barely functioning hospitals as an all-out Russian-backed assault entered its fourth day and Moscow ignored Western pleas to stop.
The Syrian government offensive to recapture all of Aleppo has been accompanied by bombing that residents describe as unprecedented in its ferocity.
Some 250,000 civilians remain trapped in the besieged, opposition-held sector of Syria's biggest city.
Hundreds of people, including dozens of children, have been reported killed since Thursday night by an onslaught that has included massive bunker-busting bombs that bring down whole buildings on people huddled inside.
The United States has called Russia's actions in support of President Bashar Al Assad "barbarism".
Moscow denies it is killing civilians said such rhetoric from the west could damage the chances of solving the conflict.
"Aleppo city's hospitals are overwhelmed with wounded people... Things are starting to run out," said Aref Al Aref, an intensive care medical worker, who spoke from Aleppo.
"We are unable to bring anything in... not equipment and not even medical staff. Some medical staff are in the countryside, unable to come in because of the siege," he said.
Western countries say Russia may be guilty of war crimes for targeting medics and aid supplies. Moscow and Damascus say they are bombing only militants. Video from Aleppo has repeatedly shown small children being dug out of the rubble of collapsed buildings.
Bebars Mishal, a civil defence worker in rebel-held Aleppo, said overnight bombardment continued until 6am (0300 GMT).
"It's the same situation. Especially at night, the bombardment intensifies, it becomes more violent, using all kinds of weapons, phosphorous and napalm and cluster bombs," Mishal told Reuters.
"Now, there's just the helicopter, and God only knows where it will bomb. God knows which building will collapse," he said. "Everybody is scared...unable to go out. They don't know what to do, or where to go."
Russia and Assad appear to have abandoned diplomacy last week, betting instead on delivering a decisive military blow against the president's enemies on the battlefield.
Capturing rebel districts of Aleppo would mark the biggest victory of the civil war for Assad, crushing the revolt in its last major urban stronghold.
Syrian government forces helped by Russian air power and militias have gradually been tightening their grip on eastern Aleppo this year. They launched the all-out assault on the city last week after abandoning a ceasefire announced earlier this month by Moscow and Washington.
Indicating there would be no respite soon, the Syrian army issued a statement reiterating its call for civilians to steer clear of rebel positions and bases in eastern Aleppo.
The Syrian Observatory for Human Rights, a monitoring body, says at least 237 people, including at least 38 children, have been killed in Aleppo and nearby countryside since the army declared the end of the ceasefire a week ago. Civil defence workers in opposition territory put the death toll at 400.
The rebel-held sector of Aleppo is completely encircled, making it impossible to receive supplies. The Syrian American Medical Society (SAMS) charity group said this week in a statement that only 30 doctors remain inside.
"We have patients who will die in the dozens if they are not evacuated," Osama Abo Ezz, a general surgeon and Aleppo coordinator for SAMS, told Reuters, speaking from an area near Aleppo.
"The medical staff is insufficient and completely exhausted. The blood bank refrigerators are completely empty. Vital medicines have almost run out. The ICU beds are insufficient and always full. The CT scanner is out of order," he said.
A Syrian military source told Reuters on Saturday that weapons were being used that could destroy rebel tunnels and bunkers, dug in during years of opposition control.
A water pumping station serving eastern Aleppo has also been destroyed. A spokesman for the World Health Organisation said a technical mission was visiting the station to assess damage.
"We don't know how long it will take to restore the functionality," said the spokesman, Tarik Jasarevic.
Rescue efforts during the bombing have been hampered because damage has made roads impassable and because civil defence centres and rescue equipment have themselves been destroyed in raids.
Hundreds of thousands of people have been killed in the civil war between Assad's government and insurgents, and 11 million driven from their homes. Much of east of the country is now in the hands of IS fighters, the enemies of all other sides.
Since Russia joined the war a year ago to support Assad's government, the administration of President Barack Obama has been engaged in intensive diplomacy with Moscow, trying to end the war between the government and most insurgent groups and turn the focus towards the common fight against IS.
But the latest escalation has left US Syria policy in tatters, all but destroying any hope of a breakthrough before Obama leaves office next year.
The collapse of diplomacy has led to dramatic stand-offs at the United Nations, where the United States called Russia's actions in Syria "barbarism" on Sunday. Moscow's UN envoy said ending the war "is almost an impossible task now".
The Kremlin said on Monday tough Western condemnation might hinder any resolution to the crisis. Moscow saw "absolutely no prospect" for holding a summit on Syria, Kremlin spokesman Dmitry Peskov said.
Moscow blames Washington for the failure of the ceasefire, arguing that the United States failed to prevent rebels from using the truce to regroup.
A spokesman for German Chancellor Angela Merkel held Russia responsible for the violence in Aleppo, saying the Syrian regime's onslaught on civilians would not be possible without military backing from the Kremlin.
"Russia must immediately end the indiscriminate bombardments of civilian areas by the Syrian government," Steffen Seibert said.
The Syrian government meanwhile pressed its efforts to pacify rebellious areas on its own terms under local agreements with besieged fighters. In Homs, another group of rebels began to be evacuated from their last foothold in the city on Monday, state news agency SANA said.
The Observatory said around 100 fighters were in the group scheduled to leave Al Waer neighbourhood for the northern Homs countryside.