A man has been killed sticking his head out of a train window.
The Gatwick Express passenger died instantly after sustaining serious head injuries near Wandsworth Common station at just after 5.30pm on Sunday.
A London Ambulance Service spokesperson told ITV News: "We were called to reports of a man hit by a train with severe head injuries.
"Sadly he was pronounced dead at the scene by doctors."
Reports by witnesses on social media said the man had been decapitated but British Transport Police (BTP) said that was not the case.
A British Transport Police spokesman told ITV News the incident happened on a Gatwick Express service on its way to London's Victoria station.
The spokesman said: "Emergency services rushed to the scene but despite their best efforts, nothing could be done to save him.
"Our investigation remains at an early stage, but initial enquiries suggest the man may have been leaning out of a train door window when he suffered a blow to the head."
"The incident is being treated as non-suspicious and a file will be prepared for the coroner," he added.
Inspector James Tyrrell from BTP said: "We are aware of a number of reports on social media which say the man was decapitated, however this is not the case.
"We are continuing to investigate the circumstances of the incident, which has been reported to the Rail Accident Investigation Branch (RAIB), and I'd urge anyone who saw what happened to contact us."
Officers are working to identify the man and inform his next of kin.
Social media users shared pictures of the scene:
- Any witnesses are asked to contact British Transport Police on 0800 40 50 40 ref 371 of 07/08/16.