The misery in a besieged rebel suburb of Damascus caused by the Syrian government’s relentless push to crush the area is indicative of a “new phase of horror” in Syria’s war, a top UN official has said.

Claims from President Bashar al Assad that his forces are doing all it can to protect civilians in the two-week-old offensive on eastern Ghouta are “frankly ridiculous”, human rights chief Zeid Ra'ad al-Hussein said on Wednesday.

The Russian-supported “indiscriminate, brutal attacks“ have killed at least 800 people and led most of the area’s estimated 400,000 population to seek shelter in basements from intense shelling and air strikes despite demands from the UN for a ceasefire on 24 February.

Scenes of devastation in Syria after deadly shelling and airstrikes and eastern Ghouta

Aid workers who entered the district briefly on Monday with the first supplies Ghouta has received this year said some residents hadn't seen sunlight for two weeks.

A ground offensive has followed the air campaign, with government forces retaking more than 30 per cent of the area of towns and farms in the last few days, seeking to split the rebel enclave into two to divide fighters.

State-affiliated al-Ikhbariya TV broadcast live shots showing dense columns of smoke rising above the town of Douma as explosions and rockets could be heard flying overhead.

Eastern Ghouta bombings: Syrian war in pictures Show all 14 1 /14 Eastern Ghouta bombings: Syrian war in pictures Eastern Ghouta bombings: Syrian war in pictures A Syrian woman and children run for cover amid the rubble of buildings. AFP/Getty Eastern Ghouta bombings: Syrian war in pictures Smoke rises from buildings following the attack on the village of Mesraba in the rebel-held besieged Eastern Ghouta region on the outskirts of the capital Damascu. AFP/Getty Eastern Ghouta bombings: Syrian war in pictures Injured children receive medical treatment. EPA Eastern Ghouta bombings: Syrian war in pictures A Syrian man carries a child injured. AFP/Getty Eastern Ghouta bombings: Syrian war in pictures An injured child receives treatment following bombings on several areas of eastern Ghouta. EPA Eastern Ghouta bombings: Syrian war in pictures A child reacts inside a hospital after relatives were injured in the bombing. EPA Eastern Ghouta bombings: Syrian war in pictures Syrian children cry at a make-shift hospital in Douma following air strikes on the Syrian village of Mesraba. AFP/Getty Eastern Ghouta bombings: Syrian war in pictures Syrian Civil Defense group extinguishing a store during airstrikes and shelling by Syrian government forces. AP Eastern Ghouta bombings: Syrian war in pictures A wounded 12-year-old Syrian boy, cries as he receives treatment at a make-shift hospital. AFP/Getty Eastern Ghouta bombings: Syrian war in pictures Syrians carry a wounded man. AFP/Getty Eastern Ghouta bombings: Syrian war in pictures An injured man covered with blood at a medical point. Reuters Eastern Ghouta bombings: Syrian war in pictures People sit a medical point in the besieged town of Douma, Eastern Ghouta. Reuters Eastern Ghouta bombings: Syrian war in pictures Syrian Civil Defense running to help survivors. AP Eastern Ghouta bombings: Syrian war in pictures Injured children receive medical treatment. EPA

Humanitarian corridors out of Ghouta monitored by Syrian ally Russia have barely been used and have become a frequent target for shelling. Both side blame the other for the violence.

The Syrian government says extremists in the besieged area are keeping civilians inside as human shields, but rebel activists say those inside will not leave for fear of repercussions when they reach government-controlled areas.

On Monday the Russian Defence Ministry offered safe passage for rebels and their families who wished to leave. While it was not clear where evacuees would be taken, in previous truce deals fighters have been bussed to rural Idlib province in the country’s northeast, the last rebel stronghold.

Rebel spokesperson Wael Olwan dismissed the offer on Tuesday, calling it “psychological warfare.”

The fate of Eastern Ghouta reflects the ‘siege, starve and surrender’ Assad playbook in several other urban battles in Syria’s complex conflict.

Scenes of devastation in Syria after deadly shelling and airstrikes and eastern Ghouta

While the region is technically covered by a 2017 de-escalation deal, the government says it is targeting al-Qaeda-linked factions in the area not covered by the agreement.

Syria’s war is entering its eighth year later this month. The fighting has killed 500,000 people and driven more than half the pre-war population of 22 million from their homes.