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.
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“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.”