Hanan Wahabi, 39, who lives on the ninth floor of the 27-storey Grenfell Tower, said she was awoken around 1:00am (0000 GMT) by smoke.
"I could see there was ash coming through the window in the living room, which was partially open," she said, sitting with her husband and son, 16, and daughter, eight, outside a local community centre.
"I looked out and I could see the fire travelling up the block. It was literally by my window," she said. "I slammed the window shut and got out."
After the family escaped, she called her brother, who lives on the 21st floor, to see if he was all right.
"The fire hadn't reached the top of the block at that point," Wahabi said.
"He said he had been told to stay inside, stay in one room together and put towels under the door. I told him to leave. He said he was going to come. Then I called him and he said there was too much smoke."
She added: "The last time I saw him they were waving out the window, his wife and children. The last time I spoke to his wife, he was on the phone to the fire brigade. I've not heard from them since, the phone is not going through, the landline isn't going through. That was about 2:00am."
A witness identified as Daniel told BBC Radio London that people on the upper floors were trapped as the flames rose higher and higher.
"People have been burned," he said. "I have seen it with my own eyes. And I have seen people jump."
Another witness named as Jody Martin said he battled his way his way to the second floor only to encounter choking smoke.
'I'm a goner'
Another survivor at the community centre, wearing shorts, a T-shirts and trainers and with a blanket draped around his shoulders, said he saved his own life with just moments to spare.
"My neighbour's smoke alarm went off and I thought he might have done some cooking," he said, giving only his first name of Eddie, 55.
"I was in bed and I heard people shout fire, fire, I opened my door and loads of smoke came in. Then two seconds later my neighbour (on fifth floor) called and said, 'Get the f*** out the building'!"
"I went into the bathroom and I got the towel and wet it and wrapped it around my head. I run out into the hallway, close the door behind me and ran for where I thought the fire exit was. I didn't find it. It was a matter of life and death -- I thought, 'If I'm in this for another five seconds, I'm a goner'."
"Then on the ground there was a fireman, he touched my leg and pulled me into where the fire stairwell was. You couldn't see anything. I just ran down the stairs. There wasn't that many people on the stairs.
"Loads of people haven't got out of the building."
Abdul Hamid, 51, lives on the 16th floor lost everything he owned but counted himself lucky to be alive.
"I have nothing. My passport was in there -- it's gone. I'm meant to be flying to Saudi Arabia for the Hajj. Now I'm homeless."