A picture taken on Feb. 20, 2018 shows a Russian air force Sukhoi Su-34 fighter jet flying over the sky in the rebel-held town of Arbin, in the besieged Eastern Ghouta region on the outskirts of the capital Damascus. (Xinhua/AFP)

UNITED NATIONS, Feb. 21 (Xinhua) -- UN Secretary-General Antonio Guterres on Wednesday called for an immediate halt of hostilities in the rebel-held enclave of Eastern Ghouta in Syria.

"I am deeply saddened by the terrible suffering of the civilian population in Eastern Ghouta, 400,000 people that live in hell on earth," Guterres told the Security Council.

Smoke rises from buildings following bombardment on the village of Mesraba in the rebel-held besieged Eastern Ghouta region on the outskirts of the capital Damascus, on Feb. 19, 2018. (Xinhua/AFP)

"My appeal to all those involved is for an immediate suspension of all war activities in Eastern Ghouta, allowing humanitarian aid to reach all those in need, allowing for the evacuation of estimated 700 people that need urgent treatment that cannot be provided there, and creating also the possibility for other civilians to be effectively treated on site," he said.

"This is a human tragedy that is unfolding in front of our eyes," said Guterres, adding that the international community should not let things go on in this horrendous way.

Syrian children cry at a make-shift hospital in Douma following air strikes on the Syrian village of Mesraba in the besieged Eastern Ghouta region on the outskirts of the capital Damascus, on Feb. 19, 2018. (Xinhua/AFP)

Syrian government troops are intensifying efforts to retake Eastern Ghouta, the last major rebel stronghold in the country.