The latest deaths brought the toll for the nearly month-old offensive to 1,350, with world powers still unable to stop one of the devastating conflict's worst crises.

Syria's war enters its eighth year with another deadly assault also unfolding in the north, where Turkish-led forces pressed an operation to seize the Kurdish-majority region of Afrin.

The operation has sent thousands onto the roads, with bombing on the city of Afrin on Friday killing 36 people and hitting the main hospital.

On the edge of Ghouta, a sprawling semi-rural area within mortar range of central Damascus, hundreds of civilians were still streaming out of destroyed towns, carrying scant belongings in bags and bundles.

Crowds crammed into a government centre on the edge of Eastern Ghouta on Friday, unsure what the next step would be after walking straight into the arms of the forces that have relentlessly pounded their homes for weeks.

- Exodus -

"We were afraid of leaving -- they had told us the army would arrest us," said 35-year-old Abu Khaled, who used to run a retail clothing shop in Ghouta.

"We reached the army and didn't find that, but now we're basically living in a camp," he told AFP.

Syria's envoy to the UN Bashar al-Jaafari said 40,000 people fled Ghouta on Thursday, and the sudden exodus appeared to have caught the government flat-footed.

Long lines formed outside the public bathrooms, and displaced families complained of a lack of access to water or mattresses.

The Syrian army in a message broadcast on state television urged all residents to use "corridors" it had established to leave the enclave, saying it had recaptured 70 percent of rebel territory.

The ground offensive pressed by Syrian troops and allied militia has splintered Eastern Ghouta into three pockets, each held by a different faction.

Those three Islamist groups said Friday they would be willing to negotiate directly with Russia on a ceasefire for Ghouta, but did not mention talks with the Syrian government.

Their statement came hours after UN special envoy for Syria Staffan de Mistura said talks were ongoing between Russia and one of the groups, Jaish al-Islam.

That negotiations track had already produced six days of calm for Ghouta's largest town of Douma, he said.

Douma has also seen deliveries of food, and hundreds of civilians have been bussed out as part of medical evacuations.

A medical source inside the town told AFP that around 60 medical cases were expected to be evacuated on Friday, in the fourth day of medical evacuations for the town.

Around 475 people, including around 90 sick and wounded, had been transported out the previous three days, the source said.

- Afrin encircled -

The Syrian Observatory for Human Rights said at least 80 civilians were killed in Russian air strikes on the southwestern Ghouta pocket on Friday.

The Observatory says it determines whose planes carry out raids according to type, location, flight patterns and munitions used, but Russia on Friday denied that its jets were taking part in the Ghouta operation.

The heaviest of Friday's raids were on Kafr Batna, where at least 64 civilians died and where the Observatory said incendiary weapons were used.

A reporter in the town contributing to AFP saw eight charred bodies in the streets and said wounded people were left in the roads as rescue centres had been put out of service by bombing.

Syrian President Bashar al-Assad has in recent months recovered swathes of territory lost at the beginning of the conflict and Ghouta was one of his key remaining targets.

An exodus of similar proportions was under way hundreds of kilometres (miles) to the north near the border with Turkey, as civilians tried to escape a looming siege of the city of Afrin.

The Observatory said on Thursday that more than 30,000 people had fled the city of Afrin in 24 hours, and another 15,000 had fled on Friday in fear a Turkish advance would cut the last exit road.

The monitor said a Turkish strike on Friday hit Afrin's hospital, killing nine people and damaging the already-strapped facility.

That brought to 36 -- at least 27 of them civilians -- the death toll in bombardment on the town on Friday, according to the Observatory.

Since January 20, Turkey and Syrian rebels launched an air and ground offensive on the Afrin region, held by the US-backed Kurdish People's Protection Units (YPG).

The UN said it was worried the forces staying inside were not allowing civilians to flee, as that would leave them more exposed to Turkey's superior firepower.

Ravina Shamdasani, spokesperson for the UN's Rights Office decried "reports that civilians are being prevented from leaving Afrin city by Kurdish forces ... (and) are being held to be used as human shields."