At least two barrel bombs have hit the largest hospital in the rebel-held eastern side of Syria’s Aleppo city, according to the medical organisation that supports it.

The facility, known as M10, had already been hit by heavy bombardment on Wednesday along with the second-largest hospital in the area in what Ban Ki-moon, the UN secretary-general, denounced as “war crimes”.

Referring to Saturday’s attack, Adham Sahloul, of the Syrian American Medical Society, said: “Two barrel bombs hit the M10 hospital and there were reports of a cluster bomb as well.”

Barrel bombs are crude, unguided weapons that kill indiscriminately.

Al Jazeera’s Charles Stratford, reporting from Gaziantep on the Turkish side of the Turkish-Syrian border, said only half of the M10 hospital was operational before Saturday as a result of previous attacks.

“We now understand it is now being put out of action completely,” he said.

The Syrian Observatory for Human Rights, a UK-based monitoring group, said one person was killed in the latest attack, but could not immediately confirm if the victim was a patient at the facility or a member of staff.

Stratford said there were reports of at least three deaths.

“We spoke to a member of the White Helmets, they said there was around 60 people inside the hospital being treated at the time,” he said.

“They say that those people have now been evacuated to a smaller clinic in this area.”

Al Jazeera’s Amr al-Halabi, who assessed the damage on Saturday, said the bodies of the victims could be seen on the hospital grounds.

“They were killed as a result of the raids,” he said. “They were patients here before the strike.”

“One of the rockets dropped just in front of the main entrance of the hospital near the emergency entrance. The hospital has suffered severe damage.”

One week into a new Russian-backed Syrian government push to capture rebel-held areas in eastern Aleppo, residents said that the city was being subjected daily to ferocious bombardment.

At least 30 civilians were killed by Syrian government or Russian air strikes overnight in Aleppo, activists told Al Jazeera on Saturday.

A further 18 were killed in air strikes on various towns in Damascus’s eastern countryside, activists said.

At least 320 people, including nearly 100 children, have been killed in Aleppo since a  US-Russian brokered ceasefire  collapsed on September 19, according to UNICEF.

Fighting has also intensified in other parts of Syria.

Civilians have been killed by shelling and air strikes in rebel-held Idlib province.

The Syrian army has launched a counteroffensive in Hama after losing territory to the rebels.

And activists say strikes have increased on residential areas of Rastan, in Homs province.

Against this backdrop of rising civilian casualties, John Kerry and Sergey Lavrov, the top US and Russian diplomats, spoke by telephone for a third straight day on Friday.

Lavrov said Russia was ready to consider more ways to “normalise” the situation in Aleppo.

However, he criticised what he called the US failure to separate moderate rebel groups from those Russia calls “terrorists”.

He argued that this allowed forces led by Jabhat Fateh al-Sham, formerly known as al-Nusra Front, to violate the US-Russian ceasefire agreed on September 9.