Aid workers and local medics have described apocalyptic scenes in the besieged city of Douma, the site of a chemical attack that has killed at least 42 people, as they scrambled to save the survivors of the latest atrocity in Syria.

Doctors, nurses and rescuers say they found themselves battling to save people who arrived from 7.45pm on Saturday bearing symptoms of a possible toxic gas attack, without medical equipment or supplies to ease their suffering.

Many of those who made it to the hospitals did not live long, they said. Those who could not be pulled out had to stay in their homes for hours as the gas dissipated before they could be retrieved, and some rescue workers also had to be treated for exposure to the alleged chemicals.

The attack, the victims of which exhibited symptoms that doctors say are consistent with exposure to organophosphorus, was only the latest salvo in a massive bombardment that began on Friday night and endured until Sunday morning, to pressure local rebels and the opposition to leave the city, surrounded by forces loyal to Bashar al-Assad.

Play Video 1:05 Aftermath of suspected chemical attack in rebel-held Douma in Syria - video

The attack came almost exactly a year after the deadly sarin gas attack in the town of Khan Sheikhun, which prompted the US to launch Tomahawk missile strikes against a Syrian airbase.

“We were 12 people, and before the attack you can imagine, we had been working perhaps 30 hours or more without stopping,” said one paramedic who treated the victims. “Then you start getting a lot of people who are suffocating, and they smell of chlorine, and imagine after all that exhaustion you get this huge number of people, around 70, targeted while they were in bomb shelters.”

He added: “We gave them whatever we had, which wasn’t much, just four oxygen generators and atropine ampoules so they could breathe … Most of them were going to die. You can imagine now our psychological state. It’s tragic. I’ve been working in this hospital for five years and those last two days, I haven’t seen anything like it.”

Another medic who treated the alleged chemical attack victims said he could no longer find the words to describe the scene. “There is no weapon that has not been used,” he said. “All the pillars of life is destroyed, even rescue workers are targeted. It’s the targeting of anything that is known to have life.”

He added: “We forget the days now, because it doesn’t make a difference any more. All the days have the same taste, the taste of death and destruction.”

It was the latest in a string of alleged chemical attacks in the enclave of eastern Ghouta, which has in the past been attacked with chlorine and sarin gas. Negotiations for the forced exile of tens of thousands of civilians and fighters from the area had broken down, due to the demands of local rebels that they stay and not be forced into leaving the region, which borders the capital, Damascus.

The negotiations resumed on Sunday after the attack.

Syrian state media denied claims that government forces had launched a chemical attack and said rebels in Douma were in a state of collapse and spreading false news, describing it as “chemical attack fabrications”.

Rescue workers said many of the victims remained where they had died because of further shelling, the penetrating odour of the toxic gas and the lack of protective gear. They said victims showed symptoms that included suffocation, central cyanosis – a blueish discolouration of the skin – foaming, corneal burns and the emission of a chlorine-like odour.

A local journalist who was nearby said: “The bombing in my area was particularly intense because there are medical points there, and the gas was dropped on a nearby building.

“The families were hysterical. I went to a medical point that is an underground hospital, and in the tunnels the dust was filling the area and there were women, children and men in the tunnels. When I arrived at the medical point it was like judgment day, people walking around in a daze, not knowing what to do, women weeping, everyone covering themselves with blankets, and the nurses running from victim to victim.

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“There were entire families on the floor covered in blankets, and there were around 40 dead in shrouds lying between the families, their smell filling the place. The situation, the fear and the destruction are indescribable.”

Douma is the last rebel position in eastern Ghouta. Nearly 2,000 civilians were killed in a two-month campaign by Assad’s forces backed by Moscow to oust the rebels from their last stronghold near Damascus. Human rights groups and UN officials have condemned the offensive, and the security council has adopted a resolution calling for an immediate ceasefire in the country’s seven-year civil war.

Tens of thousands of civilians and rebel fighters have already left other parts of eastern Ghouta for northern Syria or government-controlled areas in recent weeks, before and after rebels there negotiated surrender agreements.

