The situation of in the rebel stronghold of Eastern Ghouta near the Syrian capital is "getting worse day by day," a representative of the United Nation's children's agency said on Sunday, with children suffering amid one of the worst health crises of the Syrian war.

"Sick children desperately need medical evacuation, and many thousands more are being denied the chance of a normal, peaceful childhood," said Fran Equiza, UNICEF's representative in Syria.

The agency demanded that 137 children be allowed to leave the besieged area immediately so they could receive treatment for conditions including kidney failure, malnutrition and injuries sustained in fighting.

Long siege

Some 400,000 people have been trapped in Eastern Ghouta, the last remaining rebel-held pocket near Damascus, since 2013 amid a siege by government forces. Despite the fact that the area is technically part of a "de-escalation zone" brokered by Russia earlier this year, it has come under increased attacks since November 14 as troops loyal to President Bashar al-Assad attempt to oust opposition fighters.

The Britain-based Syrian Observatory for Human Rights, which is monitoring the now nearly seven-year conflict, says at least 202 people, including 47 children, have been killed in fighting in the fierce offensive.

UNICEF says that nearly 12 percent of children under the age of 5 in Eastern Ghouta are suffering from acute malnutrition, the highest recorded rate since the conflict broke out in 2011.

The Syrian conflict has now claimed nearly 400,000 lives. UN-sponsored talks in Geneva aimed at finding a way to end the fighting are due to resume on Monday after a short break.

tj/rc (dpa, AP)