'Wall of fire' in London bucket bomb attack

Eyewitnesses heard a loud bang and saw a "wall of fire" when a bomb went off on a packed London Underground train on Friday, with some commuters badly burned and others stampeding to the exit.

Local resident Charlie Craven was heading to Parsons Green station in west London on his way to work when he heard a "massive bang" as the device detonated.

"The first thing I saw was an orange sort of fireball encompassing the whole Tube" train, he told AFP.

"Bit like you see on 24, the TV show, or a movie sort of situation," said Craven, who works in the City, London's financial centre.

Lauren Hubbard also heard the explosion and said she saw that a "wall of fire was just coming towards us".

"It's hard to explain because it happens in an instant and you run. There were people in it of course, this fireball is just going over your head and everybody’s screaming and you just run out of the tube as quick as you can," she said.

Twitter user @Rrigs, who posted pictures of a white bucket smouldering on the train, said a "Fireball flew down carriage and we just jumped out open door".

The bucket looked like the type used by builders and there appeared to be cables coming out of it.

Twenty-people were injured in the attack -- most with flash burns, according to police.

Others were injured in the stampede during chaotic scenes at the station in a leafy and normally quiet part of London.

"We were very, very lucky," said Sally Faulding, a 51-year-old teacher who was on her way to work.

The explosion took place just as the train pulled into the station, she said, so "the doors opened automatically and everybody got out".

Like burning plastic

Louis Hather, 21, was travelling three carriages down from where the explosion took place.

"People were being trampled on. I tried to get out of the way but I could feel myself getting pushed down the stairs," he told AFP.

"I went back and got my stuff. I could smell the burning. Like when you burn plastic," the IT security worker added.

Hather's leg was cut and bruised in the stampede.

Emergency services arrived at the scene within minutes and quickly cordoned off a large area around the station located in a quiet, upper-class part of west London.

Local residents and businesses rallied together with businesses offering tea and the use of their toilets to local residents unable to get home.

The local council of Hammersmith and Fulham opened a "rest centre" nearby to help people affected.

"This is a difficult situation, people are stressed out and they need to talk to their families and for that they need battery," Lucy, the owner of an osteopathy practice on nearby Winchendon Road told AFP.

"We're just helping as we can."