The corpses and the injured arrive in a never-ending stream.

Some come by ambulance, others are piled high in the back of pick-up trucks, stacked in bloodied heaps.

Still more are brought in private cars, driven by panicked relatives who blare their horns as they roar into hospital forecourts, frantically pleading for help.

Others are carried in on foot by relatives who could not wait for transport and scooped up their loved ones, running with them in their arms or slung over their shoulders.

Men. Women. Children. Some alive, barely breathing. Others already dead.

They have gunshot wounds, head injuries, faces torn apart by pellets. Bodies so badly damaged that medics do not know where to begin. And it does not stop.

Dawn brings more. Afternoons still more. Night brings no respite. For nearly three weeks of relentless protests, the casualties of the regime’s crackdown have poured into Iran’s hospitals faster than exhausted staff can treat them.

Emergency rooms are soaked in blood. Morgues overflow. Body bags spill into courtyards because there is no space left inside.

Medics in Iran, speaking via the few patchy Starlink connections linking the country to the outside world, describe a healthcare system on the brink of collapse.

They speak of working for days without sleep. Some collapse from exhaustion. Others keep going because stopping means that patients die.

“Dead bodies and injured people – men, women and children – are arriving in trucks, ambulances and private cars,” said one medic near Tehran. “We cannot help everyone. Many died because we could not even visit them.

“People are bringing bloodied loved ones on their shoulders. Our staff are exhausted. I have not slept for days. Some of my colleagues have collapsed. We have shortages of everything. There are rivers of blood in hospitals here.

“Patients scheduled for heart and other emergency surgeries are dying. Many died.”

Asked whether all those arriving were protesters, he replied, “They are all human beings. That’s all I can tell you.”

Somewhere among the dead lies Rebin Moradi – but regime officials refuse to tell his parents where his body is.

Rebin was 17, a gifted footballer who played for a club in Iran’s top youth league. He dreamt of going professional. That dream was ended by the security forces who shot him dead on Jan 8.

His was just one of hundreds of cases overwhelming a healthcare system that was already teetering before the government began filling it with dead and injured protesters.

Graphic footage obtained by The Telegraph shows overcrowded hospital wards, pellet-riddled female corpses and medics performing CPR in hospital corridors because every room is full.

Iran’s rulers did everything they could to keep the scale of the slaughter hidden. The body bags betrayed them.

For days, the regime deployed every weapon in its arsenal to terrorise the Iranian people into silence, imposing a communications blackout across the country and threatening retribution against anyone who defied it.

Yet defy it they did. Activists, eyewitnesses and grieving relatives found ways – despite immense risk – to skirt state controls and send evidence to the outside world.

That evidence is as disturbing as it is damning. Trusted human rights organisations with longstanding nationwide networks have confirmed and verified the deaths of more than 500 people.

Senior Iranian government officials have privately suggested the true toll may run into thousands, most occurring in recent days as the regime confronts its gravest challenge since the Islamic Revolution of 1979.

The footage emerging from Iran suggests this is not only the country’s deadliest crackdown in living memory, but among the bloodiest anywhere in recent history – comparable perhaps only to the early years of the uprising against Bashar al-Assad, the Syrian dictator, or Beijing’s Tiananmen Square in 1989.

The body bags that lie row-on-row and wall-to-wall in one Tehran morgue testify to the systematic nature of the killings – a scene replicated across the country.

But it is only by zooming in that individual tragedies emerge from the statistics.

Photographs posted by opposition activists show relatives weeping over bloodied corpses in unzipped bags.

One image from Kahrizak, south of Tehran, shows a man in a yellow jacket lying on the floor, one leg outstretched, the other drawn up, clinging to the shrouded feet of a loved one as women look on, their faces etched with pity and grief.

Another shows a young woman lying on the ground beside her sister’s body, one arm draped over the shroud, her head pressed against the corpse’s cheek on the dusty floor. A man kneels nearby, offering what little solace he can.

Activists from HRANA, a US-based Iranian rights group, estimate that there are 250 bodies at the Kahrizak morgue alone.

Footage of the violence that sent so many here is starker still.

One clip, too graphic to publish, shows survivors desperately trying to save four protesters – one woman and three men – beaten or shot in the head by members of the feared Basij militia.

In the video, believed to have been filmed in Fardis, northern Iran, blood runs down a wall behind a woman lying on the street, pooling around her body. Her face is smeared red. She tries weakly to speak as a man checks her pulse. Nearby, a woman attempts CPR on a blood-drenched man. He does not respond.

Eyewitnesses say uniformed and motorcycle-mounted Basij militiamen fired live ammunition directly at protesters and chased them into alleys, shooting them as they fled.

Elsewhere, in Ilam in the west of the country, footage shows a security officer beating a prone protester before a colleague drives a motorcycle into the injured man’s head.

Even those who reach hospital are not safe. Last week, security forces stormed a hospital in Ilam, smashing through its front doors despite pleas from women inside, in an apparent attempt to arrest injured protesters and remove corpses to conceal evidence of mass killings.

It is now clear that the regime has abandoned any pretence of restraint. Witnesses describe snipers on rooftops in Tehran firing freely into crowds. The aim is no longer to disperse the protesters, but to kill them.

A battle of wills is under way. Protesters sense the ferocity of the crackdown reflects the regime’s fear and believe that the dam of terror which once constrained Iranian society has broken and cannot be rebuilt. Whether they are right, only time will tell.