One of the few remaining doctors in Aleppo has started a petition calling on President Obama and Chancellor Merkel to help end the bombing of civilians, schools and hospitals in the city.
"But their response is the same as it has been for the past five years," Dr Khatib says in his petition, "from Merkel we heard silence and from the White House our letter was met with yet another tepid condemnation - but no talk of action.
"We have seen no real effort from President Obama or Chancellor Merkel to prevent the criminal attacks against civilians and our hospitals."
Nearly 200,000 people have signed the petition so far.
In pictures: Aleppo bombing
In pictures: Aleppo bombing
1/14 Bombing in Aleppo
Smoke rises after airstrikes on the rebel-held al-Sakhour neighborhood of Aleppo, Syria April 29, 2016.
2/14 Bombing in Aleppo
A Syrian family runs for cover amid the rubble of destroyed buildings following a reported air strike on the rebel-held neighbourhood of Al-Qatarji in the northern Syrian city of Aleppo, on April 29, 2016.
3/14 Bombing in Aleppo
A man reacts as he stands on blood stains at a site hit by airstrikes in the rebel held area of Aleppo's al-Fardous district, Syria, April 29, 2016.
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The damage of the airstrikes in the rebel-held area of Aleppo on April 28
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The damaged the Medecins Sans Frontieres (MSF)-backed al-Quds hospital after it was hit by airstrikes, in a rebel-held area of Syria's Aleppo
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Syrians evacuate an injured man amid the rubble of destroyed buildings following an air strike on a rebel-held of Aleppo on April 29, 2016.
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People inspect the damage at a site hit by airstrikes, in the rebel-held area of Aleppo's Bustan al-Qasr
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A man leads a woman in tears and child out of the scene after airstrikes hit Aleppo
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Civil defence members search for survivors after an airstrike at a field hospital in the rebel held area of al-Sukari district of Aleppo
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A Syrian boy is comforted as he cries next to the body of a relative who died in a reported air strike in the rebel-held neighbourhood of al-Soukour in the northern city of Aleppo
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A Syrian family walks amid the rubble of destroyed buildings following a reported air strike in the Bustan al-Qasr rebel-held district of the northern Syrian city of Aleppo
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Syrian civil defence volunteers and rescuers remove a baby from under the rubble of a destroyed building following a reported air strike on the rebel-held neighbourhood of al-Kalasa in the northern Syrian city of Aleppo
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Syrians help a wounded youth following an air strike on the Fardous rebel held neighbourhood of the northern Syrian city of Aleppo
14/14 Bombing in Aleppo
Syrian civil defence volunteers evacuate people from a damaged building following a reported airstrike in the rebel-held neighbourhood of Tareeq al-Bab in the northern city of Aleppo
Describing the ongoing situation in Syria, Dr Khatib writes: "I am one of the very last doctors serving the remaining 300,000 citizens of eastern Aleppo.
"Atrocities are being committed every day. The Syrian regime and Russian aircraft are systematically targeting civilians and hospitals across the city."
He continues: "For five years, we have borne witness as countless patients, friends and colleagues suffered violent, tormented deaths. For five years, the world has stood by and remarked how ‘complicated’ Syria is, while doing little to protect us.
"Last month there were 42 attacks on medical facilities in Syria, 15 of which were hospitals in which my colleagues and I work. At this rate, our medical services in Aleppo could be completely destroyed in a month, leaving 300,000 people to die.
"What pains me and my fellow doctors the most is choosing who will live and who will die. Young children are sometimes brought into our emergency rooms so badly injured that we have to prioritise those with better chances, or simply don’t have the equipment to help them.
"A few weeks ago, four newborn babies gasping for air suffocated to death after a blast cut the oxygen supply to their incubators. Their lives ended before they had really begun.
"Despite the horror, we choose to be here. We took a pledge to help those in need. We have a duty to remain and help. All we ask now is for Obama and Merkel to do their duty, too.
"We do not need their tears or sympathy or even prayers, we need them to act. We need them to prove that they are the friends of Syrians."
Pictures of a dazed and bloody boy, who was rescued from the rubble of a bombed building, have become a haunting symbol of the terror those living in the city experience in their day-to-day lives.
Video shot by media activists showed five-year-old Omran Daqneesh being lifted from the ruins of a house, covered in grey dust, and placed on a seat in an ambulance.
In the footage, Omran sits alone in the chair, staring blankly ahead before wiping blood from his forehead.
Aleppo has seen fierce fighting in recent weeks, as government forces fight to secure control of the city from rebel factions.
In August, the International Committee for the Red Cross called the battle for Aleppo "one of the most devastating conflicts in modern times".
Pro-government forces, supported by overwhelming Russian air power, had managed to encircle rebels and around 300,000 civilians in the city's eastern quarters in July, leading the UN to raise the concerns of catastrophic suffering if a protracted siege ensued.
However, a fierce offensive led by thousands of rebels from outside the city broke the blockade on 31 July and fighting has only intensified since then. Both sides are bombarding their opponents indiscriminately, at a tremendous cost to both infrastructure and human life.
The main Kurdish militia, known as the People's Protection Units (YPG) controls several predominantly Kurdish northern neighborhoods.
The main insurgent groups in the city are the Nour el-Din Zenki brigade; the ultraconservative Ahrar al-Sham group; and the al-Qaida linked Jabhat Fatah al-Sham, formerly known as Jabhat al-Nusra.Reuse content