Russia has said it will consider supporting the UN-proposed ceasefire in Syria as long as it does not cover Isis and al Qaeda-linked groups.

A 30-day nationwide ceasefire is possible as long as it does not cover Isis, the Nusra Front and other groups "who are shelling residential quarters of Damascus", Foreign Minister Sergei Lavrov said on Thursday.

The UN security council is due to meet later on Thursday to discuss an emergency resolution aimed at halting the ferocious Syrian government led assault on the rebel-held enclave of eastern Ghouta. The five-day operation has so far killed more than 400 people and hit 22 medical facilities, monitors and locals say.

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

Russia, a key ally of Syrian President Bashar al Assad, has historically used its position as a permanent member of the security council to veto most UN action in Syria's war.

The Syrian and Russian air forces have been accused by various humanitarian groups of indiscriminately targeting civilian infrastructure and using barrel bombs, crude weapons filled with explosives banned under international law. Both deny the allegations.

On Thursday, the Kremlin said that Russia was not responsible for the escalating humanitarian crisis.

“Those who support the terrorists are responsible,” Kremlin spokesperson Dmitry Peskov told reporters during a conference call.

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

“Neither Russia, nor Syria, nor Iran are in that category of states as they are waging an absolute war against terrorists in Syria.”

Eastern Ghouta is technically covered by a de-escalation agreement reached by world powers last year.

The regime says al Qaeda-linked groups operating in the area are not part of the deal - raising the possibility that Russia's openness to a ceasefire deal would not include the current operation there.

In recent months the Assad government has tightened the five-year-old siege on eastern Ghouta, leaving the area’s 400,000 residents with dwindling food and medical supplies.

The new aerial attack - some of the worst violence in Syria’s seven-year-old war - appears to be paving the way for a ground assault to seize the enclave once and for all.

Rebels have responded with some of the worst rocket attacks on Damascus in years, killing 16 people.

On Thursday the UN repeated pleas to all parties for a ceasefire across the country and unfettered access for aid convoys.