Armed police have sealed off a large area in Westminster after a man in his 60s was stabbed outside the Home Office in central London.
The Metropolitan Police later said his injuries were not "life-threatening".
Scotland Yard has confirmed a 29-year-old man was arrested on suspicion of causing grievous bodily harm and possession of CS spray and has been taken to a police station.
The Reuters news agency reported that one of their photographers saw a man with facial injuries and blood on his front being led from the building.
WARNING! The following photograph may be distressing.
A police spokeswoman said there was no suggestion the incident was terrorism-related.
The police said: "Enquiries are ongoing into the exact circumstances of the incident."
The Home Office has just launched a controversial campaign, in which warnings about the dangers of carrying a knife have been printed on takeaway packaging at the UK’s most popular fried chicken emporia.