A second day of medical evacuations from Syria's Eastern Ghouta is under way, with dozens more civilians expected to be taken out of the besieged rebel enclave. 

The United Nations has called for urgent medical evacuations for more than 1,000 people who are in desperate need of treatment unavailable in the enclave.

Medical evacuations from Ghouta's largest town of Douma began on Tuesday under a deal with the rebel faction that controls it, and more sick and wounded were taken out today.

A Syrian Arab Red Crescent official in Damascus, which has facilitated the evacuations, confirmed a new operation had begun today.

Inside Douma, dozens of people awaiting evacuation gathered at a Red Crescent centre came early this morning, an AFP correspondent reported.

A high-ranking member of Jaish al-Islam, the rebel group that controls Douma, confirmed that new evacuations were taking place.

"Today, people with medical conditions will be evacuated for treatment," he told AFP.

"They are all civilians. There are around 35 people, along with their companions."

State television aired footage of Red Crescent ambulances leaving Ghouta and entering government-held territory.

The UN Security Council passed a resolution last month calling for a 30-day truce to allow for aid deliveries and medical evacuations from Ghouta.

Such evacuations in Syria have typically seen people taken out of a besieged area for care, and then returned after treatment.

Yesterday, around 150 people were transported out of Douma in the first civilian evacuation from the enclave since government forces launched a devastating offensive on 18 February.