A senior UN official has said that children waiting to be evacuated from a besieged rebel-held area of the Syrian capital city of Damascus, were being used as bargaining chips, the media reported on Thursday.

UN special envoy to Syria Jan Egeland told the BBC on Wednesday night that rebels had supposedly agreed to release government workers in exchange for the children from Eastern Ghouta.

Another 12 patients were evacuated on Wednesday, following four on Tuesday.

Thirteen more urgent cases were expected to be evacuated on Thursday.

News of the latest evacuations from Eastern Ghouta came in a tweet from the Syrian American Medical Society (Sams).

However, a doctor with Sams, Mohamad Katoub, told the BBC that it was hard to keep up with who urgently needed to be evacuated as people continued to die.

About 400,000 residents in the war-torn district have been under siege by government forces since 2013.

The main rebel group in Eastern Ghouta, Jaysh al-Islam, had said earlier that the government had agreed to the evacuations in exchange for the release of 29 of its prisoners.

Egeland told the BBC that those still in Eastern Ghouta had very little left in the way of medical facilities.

“The Syrian war has been a war against the medical profession in many ways… Too many hospitals have been bombed, have been hit on both sides, hundreds of doctors and nurses have been killed or wounded so what is left in Eastern Ghouta for the 400,000 civilians is not that much.”

Eastern Ghouta has been designated a “de-escalation zone” by the Syrian government’s main allies, Russia and Iran, along with Turkey, which backs the opposition.

But hostilities intensified six weeks ago when the Syrian military stepped up attacks in response to a rebel offensive, reportedly killing dozens of civilians.

There were also severe shortages of food, fuel and medicines, and the cold weather is threatening to worsen the hardship.

On Wednesday, the International Committee of the Red Cross (ICRC) confirmed that four critically ill people had been taken with their families to hospitals in Damascus, and that it hoped a total of 29 people would be evacuated “over the coming few days”.