A doctor has paid an emotional tribute to a leading paediatrician in rebel-held Aleppo, who was killed in a wave of bombings that left dozens of civilians dead.

Dr Hatem, director of the nearby children’s hospital, said his former colleague was among those killed in air strikes that destroyed Al Quds Hospital.

Much of the building was reduced to rubble in Wednesday night’s attack, with footage showing children’s bodies being pulled from the rubble as distraught rescuers attempted to save survivors.

Warning: This video contains distressing scenes

Dozens killed in wave of air strikes in Syria’s Aleppo

At least 27 staff and patients were killed, Dr Hatem said, saying his friend Dr Muhammad Waseem Maaz had been the area’s most qualified paediatrician.

To help as most people as possible, he worked at the children’s hospital in the day and went to Al Quds to handle emergencies at night.

“Dr Maaz and I used to spend six hours a day together,” Dr Hatem wrote in a Facebook post paying tribute to his friend.

“He was friendly, kind and he used to joke a lot with the whole staff. He was the loveliest doctor in our hospital.”

The paediatrician was reportedly planning to visit his family, who have fled to Turkey, having not seen them for four months.

The attacks inflicted significant damage on al-Quds hospital in the rebel-held area of Aleppo (AFP)

Dr Hatem said he remained in Aleppo, which faces being completely besieged by regime forces, “because of his devotion to his patients”.

Air strikes in the days leading up his death saw rockets hit metres away from the children’s hospital, causing doctors and nurses to pick up babies inside their incubators and rush them to safety on the ground floor.

“Like so many others, Dr Maaz was killed for saving lives,” Dr Hatem said, paying tribute to his “humanity and his bravery”.

“The situation today is critical - Aleppo may soon come under siege,” he added. “We need the world to be watching.”

A man leads a woman in tears and child out of the scene after airstrikes hit Aleppo (AP)

His Facebook post, put online by the Syria Campaign advocacy group, had been shared almost 23,000 times by Friday morning.

The United Nations has warned that the situation in Aleppo is “catastrophic” with the threat of more air strikes as aid deliveries to millions of Syrians are in jeopardy.

Zeid Ra’ad Al Hussein, the UN High Commissioner for Human Rights, said Dr Maaz’s death and the bombings across Aleppo and rebel-held areas of Syria showed a “monstrous disregard for civilian lives” by all parties in the civil war.

The Syria Civil Defence group has put the death toll from bombing in recent days as at least 55, including children, while the destruction of Al Quds Hospital’s cardiology, neurology and other units makes treatment for the injured even more difficult.

The facility was supported by Doctors Without Borders (MSF) and the International Committee for the Red Cross (ICRC), who both condemned the “carnage”.

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Air strikes and artillery have been raining down on Aleppo amid reports that forces are gathering on the city’s outskirts, raising fears of an assault on rebel areas by Bashar al-Assad’s forces and allies.

John Kerry, the Secretary of State, said American authorities were still gathering information but believed the hospital strike was a “deliberate” attack by Syrian forces, adding: “This follows the Assad regime’s appalling record of striking such facilities and first responders.”

A Syrian military official in Damascus denied the government had hit the hospital and Major General Igor Konashenkov said Russian planes had not flown any missions in the region for several days.

The bombardment was feared to hail the end of a fragile “cessation of hostilities” that started on 27 February excluded internationally designated terrorist groups including Isis and its rival al-Qaeda branch, Jabhat al-Nusra.