A man was arrested on suspicion of GBH after a stabbing in the street outside the Home Office in London.

The victim, a government employee in his 60s, was pictured holding a dressing to his face after being slashed in an attack outside the building on Marsham Street, Westminster, on Thursday afternoon.

The victim, who works for the Ministry of Housing, Communities and Local Government (MCHLG), staggered into the Home Office reception looking for help after being stabbed in the street, a source said.

Onlookers told how the man had "lots of blood down his front" and was led away by paramedics before being taken to a major trauma centre.

Police also cordoned off a bag outside St John's in Smith Square, where the suspect, 29, was arrested on suspicion of GBH and possession of CS spray.

The Met said: "At this early stage of the investigation, the incident is not being treated as terrorism-related, although officers are still keeping an open mind with regards any possible motive.

"Enquiries remain ongoing to establish the full circumstances of the incident."

The force said the injuries sustained by the man have been confirmed as "neither life-threatening nor life-changing".

Witnesses reported that people were approached by a man carrying knives who asked at least one person if they worked at the Home Office.

The force confirmed that an animal carrier box left at the scene contained a ferret.

Witness Gareth Milner said: “What felt like half the armed Met Police arrived on the street.”

He said that he saw a man with “lots of blood down his front” being walked away from the offices, and that there appeared to be dressing pressed to the man’s face.

Mr Milner, who works nearby for the Centre for Policy Studies think-tank, added: "Some time later a gentleman with quite a bloodied face and with dressing pressed into his face was escorted out of the Home Office by paramedics.

"He was quiet and walking on his own feet, not being physically supported."

He also said it was "a bit unnerving when the tape cordon started going up outside the entrance."

Eyewitness Guy Ellis, 54, described seeing a man remove a "long" knife from his bag before the incident.

He said: "I was sat outside the Home Office waiting for a friend to meet for lunch and on the other side of the entrance I just saw a bloke take a knife out of his bag, and just wander up the path, stop in front of two girls who were just sat there having a chat, and then he wandered back and turned round and crossed the road very calmly and merged into the crowd."

He said the knife was "long and thin" and "pointy", and described the man as 6ft, slim, with long, dark hair in a ponytail and said he was "scruffily" dressed.

An office worker opposite the Home Office, who asked to remain anonymous, described seeing a man - thought to be the perpetrator - walk calmly down the road after the incident.

She said: "He was standing over there outside the Home Office and then he was putting something away in his bag, but I didn't see a knife or anything.

"He was putting something away and then he just calmly just walked off down the road as if nothing had happened.

"Then people were being asked to go into the Home Office, they were being ushered in."

The building was put on lockdown after the incident, with civil servants told to stay inside but to "be vigilant" if they need to leave.

Communities Secretary Robert Jenrick said: "I am deeply shocked by this horrific attack on a colleague today.​ Jenrick said: "I am deeply shocked by this horrific attack on a colleague today.

"My thoughts, and those of all my staff, are with him and his family. We are ready to provide as much support as we can and we all wish him a speedy recovery.

"We will be reviewing security across the MHCLG estate. All our staff must feel safe as they go about their important work.

"I would like to give my heartfelt thanks to the police, ambulance service and our staff for their swift response today."

Home Secretary Priti Patel tweeted: “All my thoughts are with the victim and their family following horrific unprovoked knife attack on Marsham Street.”

Home Office on lockdown after stabbing incident - In pictures 15 show all Home Office on lockdown after stabbing incident - In pictures 1/15 Police officers at government building in Marsham Street in Westminster PA 2/15 Items behind a police cordon outside St John's Smith Square church in Westminster, London after an incident in which a man was stabbed outside the Home Office PA 3/15 A general view of the Home Office, after the area has been cordoned off by police following an incident Reuters 4/15 Emergency services were seen on Marsham Street around 1pm Gareth Milner 5/15 Items behind a police cordon ouside St John's Smith Square church in Westminster, London after an incident in which a man was stabbed outside the Home Office PA 6/15 The building was placed on lockdown on Thursday afternoon Gareth Milner 7/15 Items behind a police cordon outside St John's Smith Square church in Westminster, London after an incident in which a man was stabbed outside the Home Office PA 8/15 A police officer in the doorway of a government building in Marsham Street in Westminster, London after an incident in which a man was stabbed PA 9/15 Items behind a police cordon ouside St John's Smith Square church in Westminster, London after an incident in which a man was stabbed outside the Home Office PA 10/15 An ambulance at government building in Marsham Street in Westminster PA 11/15 Police officers at government building in Marsham Street in Westminster PA 12/15 EPA 13/15 AFP/Getty Images 14/15 PA 15/15 REUTERS 1/15 Police officers at government building in Marsham Street in Westminster PA 2/15 Items behind a police cordon outside St John's Smith Square church in Westminster, London after an incident in which a man was stabbed outside the Home Office PA 3/15 A general view of the Home Office, after the area has been cordoned off by police following an incident Reuters 4/15 Emergency services were seen on Marsham Street around 1pm Gareth Milner 5/15 Items behind a police cordon ouside St John's Smith Square church in Westminster, London after an incident in which a man was stabbed outside the Home Office PA 6/15 The building was placed on lockdown on Thursday afternoon Gareth Milner 7/15 Items behind a police cordon outside St John's Smith Square church in Westminster, London after an incident in which a man was stabbed outside the Home Office PA 8/15 A police officer in the doorway of a government building in Marsham Street in Westminster, London after an incident in which a man was stabbed PA 9/15 Items behind a police cordon ouside St John's Smith Square church in Westminster, London after an incident in which a man was stabbed outside the Home Office PA 10/15 An ambulance at government building in Marsham Street in Westminster PA 11/15 Police officers at government building in Marsham Street in Westminster PA 12/15 EPA 13/15 AFP/Getty Images 14/15 PA 15/15 REUTERS

The Metropolitan Police said: "Police were called at 13:06hrs on Thursday, 15 August to Marsham Street, SW1 following a report of a man with a knife at the location.

"Officers attended to find one man with knife injuries.

"London Ambulance Service attended the address where they are with the injured party.

"The injuries are currently being treated as life threatening.

"One man has been arrested on suspicion of grievous bodily harm and taken to a police station.

"Enquiries are ongoing into the exact circumstances of the incident."

A Home Office spokesperson said: “The Metropolitan Police is investigating a knife attack which took place outside the Home Office this afternoon. The victim is receiving medical care. This is a deeply concerning incident and our thoughts are with him and his family.

“As this is an ongoing investigation it would be inappropriate to comment further.”