UPDATE: The station has now reopened.
Buildings in the surrounding area have been evacuated and a police cordon is in place.
Video from the scene shows police hurriedly moving pedestrians away from the vicinity.
Scotland Yard said: “We were called at 1.40pm to reports of a security alert at London Bridge Street. Investigations continue and London Bridge Station remains closed.
“The train station has been closed as a precaution because we believe that there is a vehicle there that is suspicious.”
Police are using sniffer dogs to search the area and the fire service is also in attendance.
More to follow...