ERBIN (Syria) • Air strikes hit Syria's Eastern Ghouta region for a third straight day yesterday, bringing the civilian death toll to nearly 200 as the United Nations warned the situation in the rebel-held enclave was spinning "out of control".

Air strikes and rocket and artillery fire have battered the enclave since Sunday in apparent preparation for a government ground assault.

At least 194 civilians have been killed, among them 57 children, said the Syrian Observatory for Human Rights.

On Monday alone, 127 civilians, including 39 children, were killed in the bombardment, making it the single bloodiest day for Eastern Ghouta in four years.

Fresh air strikes yesterday morning killed at least 50 civilians, including 13 children, the Britain-based war monitoring group said.

Held by rebels since 2012, Eastern Ghouta is the last opposition pocket around the capital city of Damascus and President Bashar al-Assad is keen to retake it with an apparently imminent ground assault.

The UN's regional humanitarian coordinator for Syria, Mr Panos Moumtzis, has warned that the targeting of civilians in the enclave "must stop now".

"The humanitarian situation of civilians in East Ghouta is spiralling out of control. It's imperative to end this senseless human suffering now," he said on Monday.

The UN has repeatedly called for a month-long ceasefire across Syria's front lines, from Eastern Ghouta to the Kurdish enclave of Afrin in the north-west, which Turkey threatened yesterday to lay siege to in the coming days.

The Union of Medical Care and Relief Organisations, a coalition of international agencies that funds hospitals in Syria, said bombs had hit five hospitals in Eastern Ghouta on Monday.

"Feb 19 was one of the worst days that we've ever had in the history of this crisis," an exhausted doctor in a hospital in Eastern Ghouta told Agence France-Presse.

Dr Abu al-Yasar described treating a one-year-old baby brought into the Erbin hospital with blue skin and a faint pulse, rescued from under the rubble.

"I opened his mouth to put in a breathing tube and I found it packed with dirt," he said.

He pulled out the dirt as fast as possible, put in the breathing tube and managed to save the baby's life.

"This is just one story from among hundreds of wounded."

The bloodshed prompted the UN children's agency Unicef to issue a largely blank statement yesterday to express its anger.

"We no longer have the words to describe children's suffering and our outrage," the agency said in a brief postscript beneath the empty space on the page.

"Do those inflicting the suffering still have words to justify their barbaric acts?"

More than 400,000 people live in Eastern Ghouta, which has been surrounded by government troops since 2013. Food, medicine and other basic necessities are nearly impossible to obtain.

State media had earlier reported ongoing negotiations for the withdrawal of militants from the enclave. But the escalating bombardment suggests that the regime will likely opt for a ground assault.

It has already waged a ferocious five-day air assault on Eastern Ghouta earlier this month, leaving around 250 civilians dead and hundreds wounded.

More than 340,000 people have been killed since the civil war erupted in 2011, when protests against Mr Assad's government were brutally crushed.

AGENCE FRANCE-PRESSE, REUTERS