Smoke rises following an air strike on the rebel-held besieged town of Arbin, in the Eastern Ghouta region.

:: At least 100 civilians, 20 of them children were killed in a Syrian army bombardment of the rebel-held enclave of Eastern Ghouta, a war monitor reported in a new toll Tuesday.

Syrian Observatory for Human Rights chief Rami Abdel Rahman said the civilian death toll from Monday’s bombardment of the enclave outside Damascus was the heaviest since early 2015.

The United Nations warned on Monday that the heavy Syrian bombardment must stop immediately.

“It’s imperative to end this senseless human suffering now. Such targeting of innocent civilians and infrastructure must stop now,” Panos Moumtzis, the UN’s Regional Humanitarian Coordinator for the Syria Crisis said in a statement.

Several days of bombardment on Eastern Ghouta, near Damascus, has killed hundreds of people, with one monitor of Syria’s seven-year conflict saying that at least 77 people had died there on Monday alone.

Held by rebels since 2012, Eastern Ghouta is the last opposition pocket around Damascus and President Bashar al-Assad has dispatched reinforcements there in an apparent concerted effort to retake it.

Moumtzis, whose organization has repeatedly called for a cessation of fighting in Eastern Ghouta to allow in desperately needed food and medical aid, said the humanitarian situation in the rebel enclave was “spiraling out of control”.

“The recent escalation of violence compounds an already precarious humanitarian situation for the 393,000 residents of East Ghouta, many of them internally displaced,” he said