Image source, Getty Images

Another briefing from the Metropolitan Police will be held in the next 10 minutes, the BBC understands.

The BBC understands that a police officer who was stabbed in Parliament earlier on Wednesday has died.

Image source, Associated Press

Government sources have told BBC London there is no indication at the moment that the terror threat level in the UK will be raised. 

It has been been at severe - meaning an attack is "highly likely" since August 2014.

The next level up is critical - the highest - and means an attack is "imminent". 

Dominic Casciani
Home Affairs Correspondent

Image source, PA

The incident this afternoon outside Westminster, while at this stage unclear, is exactly the kind of scenario that security chiefs have been planning for.

Just last week there was a major counter-terrorism exercise on the River Thames as part of plans to prepare for the worst. What’s not clear at the moment is whether this incident was anything that could have been potentially foreseen – it is simply too early to know.

But the fact that the Metropolitan Police’s counter-terrorism armed response swung into action so quickly indicates how much work has been done since the killing of Lee Rigby in 2013.

In the coming 24 hours Scotland Yard’s counter-terrorism command, MI5 and, where relevant, other major agencies, will throw absolutely everything at trying to establish the background of the suspect - whether they were working alone or whether there could be more on the way.

At the same time, while they are treating this as a terrorist incident, they will know full well that they will have to test the evidence to ensure this theory is correct.

The French prime minister Bernard Cazeneuve has just confirmed that French students are among those injured in Wednesday's incident. 

Image source, PA

Just to return to the police statement thirty or so minutes ago.

People were requested to avoid the following areas on their journeys home: Parliament Square, Whitehall, Westminster Bridge, Lambeth Bridge, Victoria Street up to the junction with Broadway and Victoria Embankment up to Embankment Tube station.

The BBC's Daniel Sandford says there may have been two assailants involved in the attack on Parliament.

He says eye-witness reports have referred to a "bald white man" and a "black man with goatee beard" in association with the incident.

It is possible, although he stresses this is not confirmed, that both may have been in the car when it was driven at "high speed" down Westminster Bridge - knocking down an estimated eight people.

The car, Daniel Sandford adds, crashed into the parliamentary railings soon after. 

A woman is being treated for injuries after being pulled out of the River Thames near Westminster Bridge.

The London Ambulance Service says it has treated at least 10 people on Westminster Bridge following the incident.

A number of people are reporting that Foreign Office minister Tobias Ellwood was directly caught up in the incident inside Parliament. 

It is being reported that he came to the aid of the police officer stabbed in the Palace of Westminster and attempted to give him medical treatment.

Once again, we must say that this has not been confirmed. 

This from the BBC's Eleanor Garnier, confirming what we have already seen in several pictures. 

About 500 people including MPs are being moved from Westminster Hall in the Palace of Westminster to Westminster Abbey

We believe that they may then talk to the police to give witness statements. 

Here are some of the latest pictures from Westminster following this afternoon's incident which has left at least one woman dead.

Image source, EPA

Image source, Getty Images

Image source, Getty Images