Met Police commander BJ Harrington delivered the following statement following the incident at Westminster.
“Since 14.40 this afternoon the Metropolitan Police Service has responded to an incident in the area of Parliament Square, and the Senior National Coordinator has declared this a terrorist incident.
“And although we remain open-minded to the motive a full counter terrorism investigation is already under way - led by the Met’s Counter Terrorism Command.
“At this stage I will confirm what we know has happened, but I will not speculate.
“We received a number of different reports - which included a person in the River Thames; a car in collision with pedestrians and a man armed with a knife.
“Officers were already at the location as part of our routine policing operation. Immediately, additional officers were sent to the scene and that included firearms officers.
“We are working closely with the London Ambulance Service and the London Fire Brigade.
“I’d like to repeat our request for the public 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.
“This is to allow the emergency services to deal with the ongoing incident.
“There is an ongoing investigation being led by our Counter Terrorism Command and we would ask anyone who has images or film of the incident to pass these to police.
“We know that there are a number of casualties, including police officers, but at this stage we cannot confirm numbers or the nature of the injuries.
“Our response will be ongoing for some time as it is important that we gather all the possible evidence.
“Public safety is our top priority and we are reviewing our policing stance across London; throughout the course of this afternoon there will be additional police officers deployed across the Capital.
“I would like to ask the public to remain vigilant - and let us know if they see anything suspicious that causes them concern. Dial 999 immediately.
“The Acting Commissioner Craig Mackey is being treated as a significant witness as he was at the scene when the incident started. While he is not injured, it would be inappropriate for him to talk about the incident at this stage.
“His thoughts are with all those involved.
“Anyone with information about today’s incident is urged to call 0800 789321.”