Relentless bombing in east Aleppo has killed at least 27 people in what has been described as a catastrophic day for the besieged Syrian city.

Government troops began the new assault on Tuesday in a renewed bid to recapture rebel-held areas with “unprecedented bombardment with every type of weapon”.

Barrel bombs, mortar rounds and airstrikes fell upon rebel districts through the night according to the Syrian Observatory for Human Rights (SOHR), an independent monitoring group based in Britain.

“People went to sleep to the sound of bombardment and awoke to the sound of bombardment,” said SOHR chief Rami Abdel Rahman.

In a video posted to Facebook, civil defence organisation the White Helmets put the death toll at 38, suggesting residents were subjected to as many as 250 airstrikes and more than 2,000 artillery shells.

Dramatic footage shot by the group captured the moment rescuers drilled and digged through rubble in a nearby village to rescue a young boy as fellow volunteers frantically urged them on.

The White Helmets have struggled to keep up with calls for help since the renewed bombardment, which at times has left them unable to leave their centres because of the intensity of government fire.

“We have no more (body) bags,” said one rescue worker in another video posted by the group.

Aleppo has been divided between government control in the west and rebel control in the east since 2012. More than 250,000 people remain in the opposition-held part of the city, which has been besieged by the regime since July.

The intensity of the bombardment has forced residents to stay indoors, leaving streets all but deserted.

“This is a dark day for east Aleppo,” said Teresa Sancristoval, from the charity Doctors Without Borders. “The severity of the bombing has inflicted huge damage on the few hospitals working around the clock to provide medical care.”

The renewed assault on Aleppo ended a period of relative respite after regime ally Russia halted its strikes and organised a series of brief truces intended to convince residents and surrendering rebels to evacuate.

Syria expert Thomas Pierret said regime forces “intended to combine airstrikes with famine resulting from the siege to get rebels to surrender”, adding: “Aleppo is now completely besieged and its residents are starting to die of hunger.”