At least four schoolchildren were among eight people killed in Syrian regime shelling in Eastern Ghouta on Tuesday, despite a ceasefire in the hunger-hit rebel enclave outside Damascus.

The bombardment came as a fresh round of peace talks to end Syria's six-year war entered a second day in the Kazakh capital Astana.

Government fire on the besieged region has been on the rise for the past week, with the Britain-based Syrian Observatory for Human Rights monitor saying the latest shelling hit a school in the town of Jisreen.

"A shell fired by regime troops hit the entrance of a school in Jisreen just as children were leaving it, killing five people including four schoolchildren," Observatory chief Rami Abdel Rahman said.

A medical source at the town hospital confirmed the death toll and said another 25 people were wounded.

An AFP photographer at the medical facility saw the bodies of four children, wrapped in blood-stained white shrouds.

Several wounded children lay or sat in shock on hospital beds, including one with severed legs.

A man cried out after learning his son had died, as others around him tried to comfort him.

- Blood-stained satchels -

Small blue school bags and a tiny pair of shoes lay in a corner, drenched in blood.

Outside the primary school, children stared at the pools of blood staining the concrete ground. 

"I was coming out of school and was about to turn into a side street when the shell hit. There were dead people, wounded people," one child told AFP.

The Observatory said regime bombardment on Tuesday also hit other areas of Eastern Ghouta, where opposition fighters have been battling President Bashar al-Assad's troops for six years.

The regime on July 22 announced a ceasefire with rebels in the besieged area, which has been included in a so-called "de-escalation zone" agreed by Turkey, Russia and Iran.

On Tuesday, regime shelling on the Mesraba area, also in Eastern Ghouta, killed three civilians including one child, the Observatory said.

An AFP journalist at a morgue saw rescue volunteers and young men slip the bodies of a father and his son into white plastic bags.

"May God avenge oppressors," the man's brother cried.

In the town of Harasta, shelling also hit near a school as pupils were leaving it, wounding 10 people including five children.

On Sunday, 11 civilians including a journalist for pro-opposition television were killed in Eastern Ghouta.

- Malnutrition -

The shelling comes as Eastern Ghouta, where an estimated 400,000 people live, faces a mounting humanitarian crisis.

Shocking recent AFP images from the region showed severely underweight children, and doctors reported two infants had died of malnutrition and related complications.

On Monday, dozens of trucks carrying aid for 40,000 people entered Eastern Ghouta.

The region was once a prime agricultural region famed for its orchards.

But the rebel stronghold has been under a tight government siege since 2013, causing shortages of food and medicine, as well as price hikes for the local and smuggled supplies available.

Basic services are virtually non-existent, with electricity produced only by generators and water often dirty and a vector for disease.

More than 330,000 people have been killed in Syria since the war began in March 2011 with anti-government protests.

The conflict has since spiralled into a complex war involving world powers and Islamic State group jihadists, who took over large swathes of the country in 2014.

But the jihadists have since lost most of the territory they controlled, and were ousted two weeks ago from their de facto Syrian capital of Raqa.

They face twin offensives in the eastern oil-rich province of Deir Ezzor, from the regime and the US-backed Kurdish-Arab Syrian Democratic Forces.