Nearly two million civilians were without water in the devastated northern city after regime bombardment damaged a pumping station and rebels shut down another in retaliation, the United Nations said.

Rebel-held districts in east Aleppo came under intense air and artillery fire for a fifth night as the army prepared a ground offensive to recapture the whole of the divided city.

Saturday’s death toll of 25 was expected to rise because people remained trapped under rubble, according to the Syrian Observatory for Human Rights, a Britain-based monitoring group.

Seven people were killed in a strike as they queued to buy yoghurt at a market in the Bustan al-Qasr neighbourhood, which sits along the front line that divides the government-held west from the rebel-held east of the city.

The attack left a pool of blood and body parts strewn at the site, an AFP correspondent reported.

On Friday, at least 47 people were killed in heavy bombing, among them seven children, according to the Observatory.

There was massive destruction in several neighbourhoods, including Al-Kalasseh and Bustan al-Qasr, where some streets were almost erased by the bombardment.

Unexploded rockets were still buried in the roads in some areas, and elsewhere enormous craters had been left by the bombing.

Rescuers overwhelmed 

Residents and activists described the use of a missile that produced earthquake-like tremors upon impact and razed buildings right down to basement level where many residents desperately seek protection during bombing.

The civil defence organisation known as the White Helmets was left overwhelmed by the scale of the destruction, particularly after several of its bases were damaged in bombing on Friday.

The group says it has just two fire engines left for all of east Aleppo which, like its ambulances, are struggling to move around the city.

With no electricity or fuel for generators, the streets of Aleppo are pitch black and difficult to navigate at night, and the fuel shortage has also made it tough to fill up vehicles.

In many places, rubble strewn across streets has rendered them impassable and has effectively sealed off neighbourhoods to traffic.

On Saturday morning, the streets were nearly empty, with just a few residents out looking for bread.

The UN children’s agency UNICEF said the loss of mains supply posed serious health risks in rebel-held areas as the only alternative source of drinking water was from highly contaminated wells.

“It is critical for children’s survival that all parties to the conflict stop attacks on water infrastructure, provide access to assess and repair damage to Bab al-Nayrab station, and switch the water back on at the Suleiman al-Halabi station,” it said.