Almost 100 children have been killed, and 223 have been injured amid intense fighting that has gripped the Syrian city of Aleppo since Friday, according to UNICEF. 

The children of Aleppo are "trapped in a living nightmare," said Justin Forsyth, deputy executive director of the UN organization, in a statement on Wednesday. "There are no words left to describe the suffering they are experiencing."

UNICEF says 96 children have been killed in Aleppo since Friday. Pro-government forces, backed by Russia, on Thursday launched a massive assault to retake the city from Syria's rebels, following the collapse of a ceasefire.

Nine children were killed Tuesday during airstrikes on the rebel-held al-Shaar and al-Mashad neighbourhoods, according to the Syrian Observatory for Human Rights, which monitors the conflict. 

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Syrians react as the bodies of children are pulled from the rubble of a building following airstrikes in a rebel-held neighbourhood of Aleppo on Tuesday. (Karam al-Masri/AFP/Getty Images)

UNICEF repeated warnings that the city has only about 30 doctors left to care for the estimated 250,000 civilians caught in its rebel-held areas. 

"Children with low chances of survival are too often left to die" because of limited resources, the group said. 

Pope condemns carnage

Pope Francis decried the carnage on Wednesday, saying those responsible for the bombing must answer to God.

The pontiff expressed "deep pain and strong worry for what's happening," in his public audience Wednesday in St. Peter's Square. 

"Children and elderly … everyone is dying," Francis said.

'Rubble fell in on the patients in the intensive care unit.' — Mohammad Abu Rajab, radiologist

A major hospital was among the buildings hit in bombardments in the rebel-held eastern sector on Wednesday, residents said.

"The warplane flew over us and directly started dropping its missiles on this hospital … at around 4 a.m.," Mohammad Abu Rajab, a radiologist at the largest trauma hospital in the sector, told Reuters.

"The rubble fell in on the patients in the intensive care unit."

The strikes also hit the hospital's oxygen and power generators, and patients were transferred to another hospital in the area, medical workers at the M10 hospital said.

A bakery in another rebel-held district was also hit around 3 a.m. local time, as people lined up to collect bread, residents said.

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A wounded Syrian child is rushed to hospital after she was hit by mortar shells that targeted Aleppo's government-controlled Aziziyah and Suleimaniyah neighbourhoods on Wednesday. (Georges Ourfalian/AFP/Getty Images)

The Syrian Observatory for Human Rights said the bakery in the al-Maadi neighbourhood had been hit by artillery shelling, killing at least six people.

Earlier in the day, a senior rebel official said pro-government forces were mobilizing in apparent preparation for more ground attacks in central areas of Aleppo , which is divided into zones controlled separately by the rebels and government.

"There have been clashes in al-Suweiqa from 5 a.m. until now. The army advanced a little bit, and the guys are now repelling it, God willing," a fighter in the rebel Levant Front group said in a voice recording sent to Reuters, referring to an area where there was also fighting on Tuesday.

Another rebel official said government forces were also attacking the insurgent-held Handarat refugee camp a few kilometres to the north of Aleppo. 

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Syrian government forces gather in the largely deserted Palestinian refugee camp of Handarat, north of Aleppo, on Sept. 24. Government forces took the area following multiple Russian airstrikes. (George Ourfalian/AFP/Getty Images)

With files from CBC News