From the
BBC» Sounds gruesome....some of the tweets on this are pretty graphic
A man who is believed to have been hit by a rush hour Tube train while bending down to pick up a bag has suffered life-threatening head injuries.
Eyewitnesses on Twitter described the accident at Stockwell in south London as "horrific".
British Transport Police said the man was in a critical condition.
Nick Brown, of Transport for London, said the accident happened just before 09:00 BST and involved a train entering the Northern Line platform.
"We are investigating the incident to understand exactly what happened but we have already established that while the station was busy, the platform was not overcrowded," Mr Brown said.
A London Ambulance Service spokesman said: "We treated a man reported to be in his 20s for head injuries and he was taken as a priority to Kings College Hospital."
One Twitter user called Super D wrote that he saw the man get hit by the train "as he bent over to get his bag".
Eyewitnesses said people were screaming when they heard the impact and saw others attempting to help him before paramedics arrived.
Tube passenger Chris Duncan tweeted: "Was on this train. Awful. Man hit in the head by oncoming Tube train in horrific accident."
'Covered in blood'
Isabelle Zonderland told the London Evening Standard: "I was on the Tube when it happened. He got hit only metres from our carriage.
"When we were let off the Tube I saw him lying there. Someone who I believe was on the platform was checking for a pulse. His face was covered in blood."
In March, Nick Mann, 35, died of severe head injuries when he attempted to save his 32-year-old brother Robert from being struck by a train at Old Street Tube station.
Robert Mann remains in hospital.
On 12 March, a rush-hour passenger was dragged along Clapham South Tube station after her coat was caught in a train door.
She fell into the gap between two carriages of the Northern Line train and was taken to hospital with serious arm and head injuries.
The incident is being investigated by the Rail Accident Investigation Branch.
In 2005, Jean Charles de Menezes was shot dead at Stockwell Tube station by Metropolitan Police who mistook him for a failed 21 July suicide bomber.