The UN Security Council has voted unanimously in favour of deploying UN and Red Cross monitors to Aleppo immediately.
It is the first unanimous vote on Aleppo by the Security Council, and is designed to allow impartial actors monitor the humanitarian situation there.
The monitors will report back to the UN Secretary General in five days time detailing the safety of civilians under fire.
It comes as dozens of vulnerable orphans were among those who have been evacuated from Aleppo today as the mass evacuation effort gets back on track.
The 47 children - some of whom were in a critical condition and dehydrated - had been at an orphange near the front line but are now in rebel-held countryside west of Aleppo.
Images from Turkey-based charity the Humanitarian Relief Foundation showed some in a van at al Rashidin.
UNICEF spokeswoman Malene Jensen said they were being fed, clothed and treated by doctors, but she warned many more were still in danger inside Aleppo.
Convoys of buses were again leaving the east of the city on Monday.
Bana Alabed, the seven-year-old girl who tweeted about her experiences in Aleppo, is said to be among those who were safely evacuated.
.@AlabedBana and many children arrived to #Aleppo countryside. @sams_usa @UOSSM and partners arr coordinating the response plan there. pic.twitter.com/k3iAohYbFY
— Ahmad Tarakji, MD (@tarakjiahmad) December 19, 2016
Turkish foreign minister Mevlut Cavusoglu said 4,500 had been evacuated since midnight and some 20,000 in total.
The buses are heading to the area west of Aleppo, which is largely controlled by the rebels.
Ten buses carrying the sick and wounded also headed towards Aleppo from two besieged villages, according to the Syrian Observatory for Human Rights.
Al Foua and Kefraya are under government control but are surrounded by rebel territory and have been under heavy attack.
More than 2,000 wounded and sick people are meant to leave the Shia villages as part of the ceasefire deal.
"Complex evacuations from East Aleppo and Foua & Kefraya now in full swing. More than 900 buses needed to evacuate all. We must not fail," tweeted Jan Egeland, who chairs the UN aid taskforce in Syria
The evacuations comes a day after buses due to take people out of the area were attacked and burned.
Shia militias, fighting for the government, are demanding people be allowed to leave in exchange for the Aleppo evacuations.
The evacuations from Aleppo come after several days of delays.
People have been forced to spend several nights outdoors in freezing temperatures after the ceasefire temporarily arrangement stalled.
Thousands of civilians are still trapped in eastern Aleppo after Syrian government forces defeated rebels in the city.
Aleppo was divided between government and rebel-held areas for all of the nearly six-year-long war.
However, a rapid advance from mid-November by the Syrian army and its allies - who include Russia - forced the insurgents out of most their territory within a matter of weeks.
