A man was taken to hospital after being stabbed Thursday outside Britain's Home Office interior ministry in London.
One man was arrested at the scene, the city's Metropolitan Police said.
The Home Office is responsible for tackling crime and the government has recently launched a campaign to deter people from carrying blades in a bid to combat a surge in knife crime.
Police said they were called at 1:06 pm (1206 GMT) following a report of a man with a knife.
"Officers attended to find one man with knife injuries," the police said in a statement.
"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."
The police said the victim's injuries were not life threatening.
The London Ambulance Service said the casualty was treated at the scene and taken to hospital.
"We dispatched an incident response officer, a medic in a response car, a motorcycle paramedic and an ambulance crew," a spokeswoman said.
"We treated a man at the scene and took him to a major trauma centre."
British police officers do not routinely carry arms but armed officers were seen outside the ministry shortly after the attack.
Security cordon tape was put up around the entrance of the ministry. Security guards and police officers were stood outside.
Two police cars were stationed outside with several others parked nearby.
Home Secretary Priti Patel tweeted: "All my thoughts are with the victim and their family following horrific unprovoked knife attack."
Figures out last month revealed that knife crime in England and Wales had soared to a record high of 43,516 offences in the year ending March 2019.
The figures were up eight percent year-on-year, and up 80 percent from March 2014 when there were 23,945 offences.
For every 100,000 people in London, there were 169 knife offences in 2018-19 -- way ahead of the figures for the rest of England.
New Prime Minister Boris Johnson reiterated his commitment to tackling the "scourge" of knife crime as he took questions from the public live on Facebook on Wednesday.