The blaze, which started in the roof, turned the side of the building into a burnt-out shell, sending a massive black cloud into the sky.

Patients, some wearing oxygen masks, were wheeled out into the street in their sick beds while mothers were forced to leave clutching young babies.

VIDEO of #Istanbul hospital fire emerges online https://t.co/wgvcnPkfK3 pic.twitter.com/U1c1xElObn

— RT (@RT_com) April 5, 2018

Firefighters used elevation lifts to try to extinguish the fire at the top of the multistorey hospital building in the Gaziosmanpasa district of Istanbul.

However local officials said there were so far no reports of casualties although some patients may have been affected by the smoke.

Speaking at the scene, Istanbul governor Vasip Sahin said the fire services had managed to bring the blaze partly under control.

Officials evacuate a patient following a fire at a hospital in Istanbul. Picture: AP /Cavit OzgulSource:AP

Echoing comments by other officials, he said there were no current reports of casualties. “So far there is no sad news. God willing, it will stay that way,” he told the crowds outside in comments broadcast by television.

Massive fire erupts in a hospital in Istanbul, Turkey, evacuation underway pic.twitter.com/B4n2JI7Xfa

— Khalid (Halit Ertuğrul) (@khalid_pk) April 5, 2018

Witnesses told Turkish television that the flames spread rapidly around the side of the building.

“The fire was knocking against the windows. It was terrifying,” one woman told CNN-Turk, without giving her name.

#BREAKING: A Fire has erupted at a hospital in #Istanbul’s #Gaziosmanpaşa neighbourhood in #Turkey. pic.twitter.com/d8Sb6Lns2S

— EHA News (@eha_news) April 5, 2018

Sahin later told reporters said that the fire had been on the outer part of the building — rather than the inside — but a “lot of smoke” had penetrated inside which emergency services were now seeking to expel.

He added that some 70 patients had been evacuated outside and those in intensive care moved to a secure place inside the hospital that was not affected.

There was no immediate information on the cause of the blaze but Sahin said that two prosecutors had already been tasked to investigate.