A desperate mother shouted "Help me! Help me" after fire broke out in her house killing two of her sons aged two and three, neighbours said.
One would-be rescuer was beaten back by the smoke and flames at the semi-detached home in Alder Street, Huddersfield, and the toddlers were recovered by firefighters.
The boys, named on floral tributes as Jake and Logan, were rushed to Huddersfield Royal Infirmary on Saturday afternoon but could not be saved.
Their mother and an older brother had managed to flee the house before firefighters arrived.
The fire was believed to have started in the front bedroom and a rescuer, thought to be a neighbour, tried to get in by climbing on a veranda at the back of the house.
The boys' father also dashed to the house to try to help, neighbours said.
It is not known if smoke alarms were fitted to the privately rented house, the family moving into the property around six months ago according to neighbours.
The family's next door neighbour, who did not want to be named, said the mother was shouting, "Help me! Help me!", crying and screaming for help.
"We saw the smoke everywhere, a man tried to climb up to help but there was too much smoke, you could not see anything," she said.
"I asked the man he said two children were still inside.
"Then the police and fire brigade came and they went inside."
The neighbour said she then saw one of the children brought out from the property and laid on the ground.
She added: "They tried to make him breathe, really trying. He was all black from the smoke.
"It's really shocking, everyone is in shock. My children were upset."
Next door neighbour Shaveta Sharma rushed home from work after a friend rang to say her neighbour's house was on fire.
She arrived as the fire service got there as did the children's father.
Ms Sharma said: "Within four or five minutes, one of the children, they brought him out. They were giving him first aid, CPR, they were really trying hard.
"I was just trying to reassure mum, she was proper panicking to see her child in that state.
"We were just praying to God at that time, the child should be safe.
"Within a couple of minutes they have controlled the fire. The other child, emergency services they treated that child in the cot. That's what mum told me, one child was in the cot.
"They said they were treating him inside. They took 35, to 40 minutes in the house.
"It's very, very tragic. You can think, a mum and dad lost their two children suddenly, it's really awful.
"We were telling mum to calm down, she was stressed, crying, shouting. She came out of the house and she was screaming in the road."
She added: "Everybody is really sad today, everybody is just quiet, not saying anything at all. We don't know what to say to (the) parents."
Family members have returned to the scene of the tragedy to leave flowers.
West Yorkshire Police said the cause of the fire was not thought to be suspicious.
Chris Kirby, group manager at West Yorkshire Fire and Rescue Service, said firefighters with breathing apparatus brought the boys out.
He said: "(It's) an absolutely tragic event and our thoughts are with the family affected, clearly it's going to be devastating for them, the local community and there's also an impact on the crews who attended.
"I was speaking to some of them yesterday, they had got tears in their eyes, they were very upset about the scenes that they had witnessed."
Local Labour councillor Amanda Pinnock, who was leafleting in the area on Saturday, said the community was in shock.
"It's a tragedy," she said. "It's a very close-knit area in Fartown."
She urged people to get a smoke alarm and to check them regularly.
"The fire service will come and fit them for free," she said. "It's crucial people get them."