One man has been detained at the scene.
Metropolitan Police said they were called to Exhibition Road near the Natural History Museum just after 2.20pm.
A spokesman for the force said: “It is believed that a number of pedestrians have been injured.
“Officers are on scene, and the London Ambulance Service have been called.
“A man has been detained at the scene.
“Enquiries to establish the circumstances and motive are underway.”