The Home Office in Westminster is on lockdown after a “man in a suit” was stabbed outside.
Armed police are at the scene and a cordon has been put in place, after it is reported the victim headed into the building for help.
Witnesses reported seeing a man with a “bloodied face” being led out by paramedics.
Others said there are “bloody tissues in the entrance hall.”
Police say there is no suggestion the incident is terrorist-related.
There are unconfirmed reports that the victim, who has been left with life-threatening injuries, was a member of Home Office staff.
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Another witness claims a “man in a suit” was stabbed outside and made his way into the headquarters, on Marsham Street, for help.
Police officers on motorbikes and paramedics arrived at the scene at around 1.20pm.
Witnesses at the scene say the person who stabbed the victim ran off.
The victim was seen being brought out and taken away in an ambulance.
An eyewitness at the scene said: “The gentleman who was escorted out by paramedics looked to have a black shirt partially on, with blood down his front (possibly from his face).
“It looked like his clothing had been removed to possible check for other injuries”
Metropolitan Police and the Home Office have been approached for comment.
A police spokesman said: “Police called at 13:06 to Marsham Street, Westminster following a report of a man with a knife.
“Officers attended to find one man with knife injuries. London Ambulance Service attended where they are currently with the injured man. One man arrested and is in custody. More to follow.”
The building has not been evacuated.
The Home Office is a ministerial department responsible for policing in England and Wales, fire and rescue services in England and visas and immigration and the Security Service.
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