A murder inquiry has been launched following the stabbing of a man on board a train in Surrey.
British Transport Police (BTP) said officers were called to Horsley station at 1.15pm on Friday to reports of an attack on the 12.58pm train service travelling between Guildford and London Waterloo stations.
Officers from Surrey Police and South East Coast Ambulance Service also attended the incident in which the victim suffered a "fatal stab wound".
BTP said the injured man died at the scene of the "frightening" attack.
A number of police officers remain in the Clandon area and are attempting to identify and trace the man responsible for the assault.
No arrests have been made at present, police said.
Detective Superintendent Gary Richardson from BTP said: "This was a shocking and violent attack which took place on board a train in broad daylight.
"Officers from BTP are with the family and have deployed a specially trained family liaison officer to support them through this difficult time.
"We know that this was an incredibly frightening incident for passengers travelling on the train.
"We believe that the suspect and victim boarded the train at London Road at 1.01pm and we would encourage who was on this train to come forward regardless of whether or not they think they can help our investigation.
"We believe the suspect departed the train at Clandon station.
"Passengers and members of the public can expect to see an increased presence by BTP and Surrey Police officers at Horsley and Clandon as our inquiries continue.
"We would advise anyone in the local area who sees anyone they think maybe the suspect to contact 999 immediately."