A police officer was attacked by a knife-wielding man near Parliament while "multiple" people were struck by a car on Westminster Bridge.
The House of Commons has suspended its sitting and Theresa May was bundled into a car by plain-clothed police.
An air ambulance later landed in Parliament Square and several people are believed to be injured.
Express.co.uk was alerted to the incident by a series of blasts before a group of people were seen running towards Parliament from Westminster Bridge.
A handful of people then entered the parliamentary estate before one appeared to repeatedly attack a police officer with an implement.
Journalists in the press gallery were told to stay inside offices and keep away from windows as security officers dealt with the incident.A Met Police spokesman, said: "Police were called at 14.40 to a reports of an incident on Westminster Bridge.“It’s being treated as a fire arms incident. Officers are on the scene and dealing.”More to follow...