Over 30 children killed in Eastern Ghouta in the first two weeks of 2018

"It is shocking that only in the first 14 days of the year more than 30 children have been killed in escalating violence in east Ghouta, where an estimated 200,000 children have been trapped under siege since 2013," read a statement by UNICEF Representative in Syria, Fran Equiza.

"UNICEF received information from inside East Ghouta that people are taking shelter underground in fear for their lives. One particular heavy attack on residential buildings was so strong it reportedly injured 80 civilians including children and women. Medical personnel struggled to pull survivors out of the rubble."

The statement added that two medical facilities had come under attack in the past days, with most health centres having to close.

Around 400,000 people are believed to be trapped in the besieged area, with the UN having previously appealed for the Assad regime to allow the evacuation of around 500 priority patients.

Jan Egeland, the UN's humanitarian adviser for Syria warned last month that "the number is going down, not because we are evacuating people, but because they are dying."

From the list of 500 urgent cases announced last year in November at least 16 have already died for lack of medical assistance.

Hospitals in Eastern Ghouta are ill-equipped to deal with the increasing humanitarian needs, and the escalating violence has left hospitals and healthcare centres damaged, "severely limiting medical care for people at a time when they need it most." 

In Idlib, the report added, the maternity and paediatric hospital was struck three times, taking it out of service and leaving at least one patient and two medical staff dead.

Late last year, the International Committee of the Red Cross hoped that it would be able to resume evacuations of those critically ill in Syria's largest siege in rebel-held Eastern Ghouta.

Following long negotiations with the Assad regime, medical charities were able to begin evacuating priority medical patients after a deal was struck between Damascus and a rebel faction.

Patients were evacuated from rebel-held Eastern Ghouta in return for the rebels releasing detainees.

But international aid agencies have voiced concern over the terms of the deal.  

"It is a not a good agreement if they exchange sick children for detainees, that means children become bargaining chips in some tug of war," the UN humanitarian adviser said.

The region east of Damascus has been under near-daily bombardment and a crippling regime siege since 2013, but rebels controlling the area have been able to use it as a launch pad for rocket and mortar attacks on the capital.

The beleaguered 100-square-kilometre enclave's estimated 400,000 inhabitants are suffering severe shortages of food and medicine.

Children there are particularly vulnerable to malnutrition. A shocking report late last year by the World Food Programme found that Syrians are eating animal refuse, fainting from hunger and forcing their children to eat on alternate days in 'coping strategies'.

"What does the world need to take collective action to end the war on children in Syria? When will those who are fighting realise that by killing children they are also killing Syria's future?"

UNICEF reiterated that it "will continue providing humanitarian assistance" to the children of Syria, adding that "we can, and must do better."

Rights groups, including Amnesty International, have accused the Assad regime of using illegal cluster munitions on the besieged enclave.

Eastern Ghouta is one of the last remaining opposition strongholds in Syria. Recent weeks have seen an increase in violence and aid groups have expressed "grave" concerns over the deteriorating situation in the region.

The Syrian conflict began when the Baath regime, in power since 1963 and led by Assad, responded with military force to peaceful protests demanding democratic reforms during the Arab Spring wave of uprisings, triggering an armed rebellion fuelled by mass defections from the Syrian army.

The brutal tactics pursued mainly by the regime, which have included the use of chemical weapons, sieges, mass executions and torture against civilians have led to war crimes investigations.