The push on Friday signalled the collapse of a 10-day ceasefire over a potential deal to evacuate opposition fighters from the besieged enclave on the outskirts of the capital, Damascus.
According to the Syrian Civil Defence, a group of rescuers operating in opposition-held areas in Syria, the air raids killed at least 30 civilians, including women and children.
Live TV footage showed thick smoke billowing from different parts of Douma.
Amid massive destruction, @SyriaCivilDefe teams work to evacuate the injured civilians after the renewed bombardment on their residential neighbourhoods of #Douma City #EasternGhouta. So far more than 30 civilians have been killed in the barbaric attack. Rescue efforts continue. pic.twitter.com/tCmptDlJI1
— The White Helmets (@SyriaCivilDef) April 6, 2018
Syrian government forces said they retaliated after a faction within Jaish al-Islam, the rebel group controlling Douma, shelled a government-held area, killing four people.
Jaish al-Islam, the last remaining rebel group in Eastern Ghouta, denies the accusation.
The group had been in Russian-brokered negotiations with the Syrian government for the past several days.
Tens of thousands are estimated to be remaining in Douma.
United Nations spokesman Stephane Dujarric said the renewed outbreak of fighting in Douma “is of great concern to us”.
“There are still a number of people who are besieged and trapped in the area,” he told reporters at the UN headquarters in New York.
He added that is “a violation of international law” to target civilian infrastructure and civilians.
Last week, two rebel groups reached evacuation deals with the Russian army, which resulted in about 19,000 people leaving for the northern province of Idlib.
They included fighters from the Faylaq al-Rahman and Ahrar al-Sham rebel groups, their families and other residents.
Rebel groups argued that the evacuation amounts to forced displacement, but gave in after weeks of intense bombardment.
The evacuation agreements followed a Russia-backed government offensive in February and March that killed hundreds of people in Eastern Ghouta.
To date, an estimated 150,000 residents of Eastern Ghouta have evacuated to northern Syria.