Doctors in Aleppo are “ready to die”, a medical charity official has said after the largest hospital in the rebel-held area of the Syrian city was destroyed by multiple air strikes.

The attack on the trauma centre comes amid a sustained assault by pro-Assad forces backed by Russian warplanes.

Air strikes across the eastern part of the city overnight killed 30 civilians, activists told al-Jazeera, and the attacks continued throughout the day.

The medical charity, Medecins Sans Frontieres (MSF), said there had been a “bloodbath” in the city.

The largest hospital in the Aleppo, codenamed M10, was hit by two devastating barrel bombs – improvised weapons that are cheap to make – rendering the area’s biggest medical facility completely out of use.

At least one rocket and two cluster bombs also hit the hospital, according to the Syrian American Medical Society.

Two patients in the hospital were reportedly killed and 13 more injured in the attack and a number of people were believed to be trapped.

It was not immediately clear who was responsible for the attacks, but hospital facilities have been plagued by bombing by forces loyal to the Syrian government in recent weeks.

Pablo Marco Blanco, operations manager at MSF, told The Independent the loss of the M10 hospital was significant.

“There is only one hospital left in East Aleppo that has substantial capacity – this is what we are most worried about now,” he said.

Speaking about morale of the doctors to whom he had spoken, he said: “Most of them are ready to die.

“They are aware of this [the dangers] and they are willing to stay there until the end.”

The fighting has intensified after a US-Russian brokered ceasefire collapsed and diplomatic efforts came to a halt.

Describing the attack on M10, Adham Sahloul, of the Syrian American Medical Society, told news website TRT World: “There were direct hits to the hospital.

“There were two barrel bombs, reportedly two cluster bombs and at least one rocket of some sort that hit the hospital directly.

“It created immense damage to the facility, destroyed all the windows. It rattled all the staff and the patients there.

“As of now there’s no idea as to when it can be brought back into operation. The facility is extremely damaged.”

Mr Sahloul said a group of patients and doctors “were inside the hospital for basic triage, bandaging, and cleaning services for emergency cases” when the bombing started and had been trapped in the wreckage.

Hospital administrator and radiologist Mohammad Abu Rajab made an emergency call for help on Saturday morning from inside the M10 hospital.

“The hospital is being destroyed! SOS, everyone!” he said in an audio message given to journalists.

The M10 hospital was also attacked on Wednesday, along with another called M2. Codenames are used in an attempt to keep their locations secret because of the threat of attack.

The Syrian Observatory for Human Rights said air strikes also hit a smaller field hospital in the Sakhur neighbourhood of Aleppo on Saturday.

“One person was killed and the field hospital is out of service,” observatory head Rami Abdel Rahman told AFP.

The besieged old quarter of Aleppo was bombed heavily by Russian war planes during the attacks.

Air strikes concentrated on supply lines to rebel-held areas such as the Castello Road and Malah district, Reuters reported. Fighting also raged in the Suleiman al-Halabi neighbourhood.

France has condemned the latest attack on the M10 hospital as a war crime and said the “perpetrators will be held accountable”.

Rights groups have said the hospital attacks are part of a deliberate strategy to target civilian infrastructure and therefore constitute war crimes.

The recent surge in attacks in Aleppo by forces loyal to President Bashar al-Assad have been among the most deadly in the country’s five-year civil war.

A traumatized toddler clings onto a nurse at a SAMS hospital in Aleppo

A video posted on social media on Friday showed a traumatised toddler holding onto a nurse following an air strike in Aleppo.