Syrian doctors in the besieged eastern half of Aleppo said Tuesday a plan to evacuate sick and wounded residents failed because the UN was unable to guarantee the patients' safety.
The United Nations and key medical groups held days of talks aimed at securing the safe passage of the critically injured or ill during a three-day Aleppo ceasefire announced by Russia, to no avail.
The UN on Monday said the plan was aborted for several reasons, "including delays in receiving the necessary approvals from local authorities in eastern Aleppo".
But doctors inside the war-ravaged city said the UN was also at fault.
"Of course we blame the United Nations for not providing a clear plan," said doctor Hamza al-Khateeb, spokesman for nine leading doctors in eastern Aleppo.
"We need guarantees that there will be no arrests or attacks on the sick, wounded, and their companions," he told AFP from inside the city.
"There was no clarity on the meeting points, on which cars would transport them, or on whether they would be searched."
The uncertainty meant the doctors did not provide the UN with the names of candidates for medical evacuation.
The UN's humanitarian coordination agency in Geneva had no immediate comment, but on Monday UN humanitarian aid coordinator Stephen O'Brien accused both regime and rebels of holding up the evacuations.
He said rebels imposed conditions to guarantee the safety of the evacuation while the Syrian government refused to allow medical and other aid supplies into the rebel-held east.
One of east Aleppo's last paediatricians, doctor Hatem, who declined to give his last name, said he and fellow doctors had demanded guarantees evacuees would be safe.
They also sought an end to bombardment, aid deliveries, and reinforcements for Aleppo's exhausted medical staff.
"The UN contacted me as a paediatrician to ask me for children's names. I told them there's no problem as long as you give us the conditions we asked for," he told AFP.
"To each of these conditions, they told us, 'We'll see in the future.'"
More than 250,000 people remain in eastern Aleppo, which has been under government siege since July and faced heavy regime and Russian fire since Damascus began an operation to recapture the city.
Russia's three-day truce was meant to encourage civilians and rebels to leave the east, but only a handful did so.
The powerful Nureddin al-Zinki faction also said it had sought "written guarantees from the United Nations that the wounded and their companions would not be detained, arrested, killed, or insulted."
"Until this moment, we have not received any responses, either positive or negative, on the previous points -- only verbal promises to study the points and respond," political officer Yasser al-Youssef said.