Details of the fire are emerging, with five people also known to have been injured and taken to hospital.
Five ambulance crews and a helicopter were sent to Tollgate Road in Beckton after it was reported to emergency services at 17:26 BST on Thursday afternoon.
Firefighters from the London Fire Brigade along Police and Paramedics have been scrambled to a fatal property on Tollgate Road in Beckton East London this afternoon.
A number of resources from the Fire and the London Ambulance Service have been called to assist at the well-developed blaze in the three-storey property that broke out just on Thursday afternoon.
Flames can be seen licking the window of the third floor.
Witnesses claim that a number of people have been seen jumping from the building:
There was a bit of smoke, and one of my colleagues said, ‘call the police,'” said the manager of the Lidl across the street. That’s what I saw as soon as I stepped out of the shop – a massive fire.
It was mostly on the balcony and then the entire house.” People were jumping out the windows from the top balcony, and people were running around everywhere.
“They had a mattress there and were attempting to jump on it, but some people were unable to reach the mattress.”
He doesn’t know how many people escaped, only that “a couple” did.
The London Fire Brigade has sent an aerial ladder platform along with six fire engines to assist fire crews.
Road Closures within the area have been put in place and local bus services have been out on divert and drivers are being asked to avoid the area and seek an alternative route.
The LFB, London Ambulance Service and The Met Police have been approached for comment
A spokesperson for the LFB said: Firefighters have been called to a flat fire on Tollgate Road in Beckton.
The first floor and second floors of the residential block are alight. The staircase from the first to the second floor is also alight.
The Brigade was called at 1724. Six fire engines and around 40 firefighters from East Ham, Plaistow, Barking and surrounding fire stations are at the scene.
The cause of the fire is not known at this time.
Police were called at approximately 17:28hrs on Thursday, 6 April to reports of a fire at a block of flats in Tollgate Road, E6.
Police, LAS and LFB are currently at the scene dealing with the fire.
It is believed that there has been one fatality and number of others injured. No further details at this stage.
Enquiries into the cause of the fire are ongoing.
A road closure is in place on Tollgate Road and restriction are in place on Bradley Stone Road and Valiant Way, E6.