A man has been arrested on suspicion of causing grievous bodily harm after a man was stabbed close to the British Museum, the Metropolitan Police said.
The museum was evacuated and police said it was not terror related and there was “no outstanding risk to the public”.
The man was stabbed in the arm and taken to hospital.
The museum is now open to visitors again.
A statement said: “The museum has now reopened with raised security including a heightened search operation.”
Police said the incident happened at junction of Great Russell Street and Museum Street which is immediately outside the entrance of the famous museum in central London.
A police tent was erected on the pavement on the museum side of Great Russell Street, just metres from the entrance.
London Ambulance Service said its medics treated the man at the scene for his arm injury “before taking him to a major trauma centre as a priority”.
A 27-year-old American woman said she was about to enter the museum queue when she was told to leave by police because someone had been stabbed.
The visitor from New York was leaving a Starbucks across the road when police approached her.
She said: “I was standing across the street at the Starbucks walking out to get into the line.
“We decided it was a good time to go, then we walked out and a cop directly in front of us told us we needed to leave and that the crime scene was large.
“I heard that someone was stabbed and the ambulance was parked inside near the grass area and then rushed down the street, right by me, with police following behind.”