British police said they had carried out a controlled explosion on Wednesday near the new but still unoccupied US embassy building in south London, after being called to a report of two unattended vehicles.

"A controlled explosion was carried out at around 17:37 pm (1637 GMT)," a statement said, adding: "Specialist officers are at the scene and cordons have been put in place. The London Ambulance Service and the London Fire Brigade are also in attendance."