The tots – all of whom are believed to have been related and aged under five – were killed when a blaze broke out in Sutton last night just before 7pm.
The first hero firefighters on the scene were faced with an “intense” blaze across the entire ground floor of the mid-terrace home.
In spite of the inferno, they bravely rushed inside and rescued the little ones.
They then gave them CPR on the street outside until paramedics arrived.
However, all four children were pronounced dead when they were taken to hospital.
The fire raged from 6.55pm until 8.35pm, with 60 crew members called out to battle the flames.
The cause is not yet known, and no arrests have been made.
London Fire commissioner Andy Roe said in a statement last night that those who attended were “numb” at the tragedy.
‘WE ARE NUMB’
“This is an incident that has left everyone numb with profound sadness,” he said.
“My thoughts are with the family and friends of the children, the whole local community and all those who will be affected by this fire.
“Fire crews arrived quickly and located the children inside the property.
“They were brought out of the house and given immediate emergency care.
“The welfare of our staff involved in this incident is very important to us and all of them will be offered counselling as a priority.”
Superintendent Rob Shepherd of the Met Police said: “The thoughts of everyone at the South Area Command Unit are with the family and friends of these four young children, who have suffered such a devastating and tragic loss last night.
“I know these sentiments will be shared by the local community, Sutton and London as a whole.
“We remain on scene with our emergency service colleagues and will be working through the night and beyond.
“At this very early stage the cause of the fire is unknown and will be investigated.”
Graham Norton, assistant director of operations at London Ambulance Service, said resources including advanced paramedics, members of the Hazardous Area Response Team and two trauma teams attended.
“We treated four children at the scene and took them to hospital,” he said.
“Our thoughts are with the family and friends of the four young children and everyone affected by this devastating tragedy.
‘SO SAD AND UNREAL’
“Thank you to all the ambulance crews and our colleagues in the fire brigade and police, who all worked so tirelessly to try to save them.”
Residents warned the road was blocked at around 7.20pm – and dozens have now spoken of the “awful” loss.
Speaking before the extent of the horror was known, one wrote: “Heartbreaking
“I really hope they all make it.
“I’m praying so hard the kiddies are ok.”
A neighbour wrote: “An ambulance has just gone past with blue lights on.
It’s so sad and unreal seeing all the blue lights. So heartbreaking.”
Another local resident said: “So sad. “You can smell the burning in the air.”