A police officer has been stabbed in the Houses of Parliament in central London.
He told MPs the “alleged assailant was shot by armed police” following a “serious” incident.
Staff inside Parliament were told to stay inside their offices.
It is claimed the attack was shot up to four times.
Tom Peck, political editor for the Independent, tweeted: “There was a loud bang. Screams. Commotion. Then the sound of gunshots. Armed police everywhere.”
Scotland Yard said it was called to a firearms incident on Westminster Bridge amid reports of several people injured.
Transport for London said Westminster underground station has been shut at the police’s request.