What is happening in Aleppo is worse than "a slaughterhouse", UN Secretary General Ban Ki-moon has said.
Two hospitals in besieged east Aleppo were hit by Russian and Syrian air strikes on Wednesday, amid a renewed assault on the city.
Seven people were killed and at least one of the hospitals is out of service following the bombings, which also hit a bread distribution centre.
The Britain-based Syrian Observatory for Human Rights said six people were killed outside the bread distribution centre.
Speaking to the UN Security Council just hours after the hospitals had been bombed, Mr Ban implicitly accused Syria and Russia of committing war crimes.
"Let us be clear: Those using ever more destructive weapons know exactly what they are doing. They know they are committing war crimes," he said.
Syria's government is conducting a major offensive in Aleppo in a renewed attempt to take back rebel-held neighbourhoods after a US-Russia ceasefire broke down.
"Imagine the destruction," Mr Ban continued. "People with their limbs blown off, children in terrible pain with no relief, infected, suffering, dying. With nowhere to go and no end in sight.
"Imagine a slaughterhouse. This is worse. Even a slaughterhouse is more humane."
Mr Ban urged the Security Council to take "decisive steps" to protect health facilities and medical staff.
Russia's deputy UN ambassador Evgeny Zagaynov told the council that Syria and Russia are being blamed for "the majority of strikes on civilian facilities in Syria" - including Wednesday's hospital bombings in Aleppo - without any independent investigation and verification.
He said similar unacceptable incidents have resulted from "the destabilizing policy carried out by the US and its allies," and cited last October's US military attack on a Doctors Without Borders trauma hospital in the Afghan city of Kunduz which killed 14 staff and 28 patients and caretakers, noting that although the US took responsibility, those responsible are still at work.
At least 96 children have been killed and 223 injured since last Friday, the UN children's agency said on Wednesday.
Children in the city are "trapped in a living nightmare," UNICEF deputy executive director Justin Forsyth said, adding that the shock and suffering among children "is definitely the worst we have seen".
Additional reporting by agencies
