It has been reported that a man has launched an attack outside the Houses of Parliament in London, with politicians and journalists tweeting about hearing loud crashes outside the building.
According to reports, witnesses said they saw people being treated for wounds and that a man was seen wielding a knife in the grounds.
Commons Leader David Lidington confirmed a police officer has been stabbed.
Staff inside Parliament have been told to stay inside their offices.
MPs claimed they heard ‘three or four gunshots’.
The attacker is reported to have mowed down several pedestrians as he drove a grey Hyundai car across Westminster Bridge before crashing it into railings and emerging from the crash to stab a police officer.
Tom Peck, political editor for the Independent, tweeted: "There was a loud bang. Screams. Commotion. Then the sound of gunshots. Armed police everywhere."
Meanwhile the Metropolitan Police tweeted: “We were called at approx 2:40pm to reports of an incident at #Westminster Bridge. Being treated as a firearms incident - police on scene.”
Police are asking people to avoid the following areas: Parliament Square; Whitehall; Westminster Bridge; Lambeth Bridge; Victoria Street up to the junction with Broadway and the Victoria Embankment up to Embankment tube.
Transport for London has also confirmed that Westminster underground station has been shut.