Christian and Conservative MP David Burrowes spoke to Premier via mobile phone from the Palace of Westminster where he and other members had been told to stay inside amid a lock down.
Mr Burrowes said: "There was a car that did mow down a pedestrian and that car, I think, was linked to someone who was wielding a knife and managed to force their way through the gates of the Palace of Westminster and into the outside area of the courtyard."
Several pedestrians were moved down on Westminster Bridge by a man driving a grey Hyundai i40 before the vehicle crashed into railings and drove through the gates.
Scene at Lambeth Bridge a short time ago. Millbank cordoned off after major terror alert at Palace of Westminster. Details still emerging. pic.twitter.com/vZH9VM4pys
— Alex Williams (@AlexWpremier) March 22, 2017
The man got out of his vehicle and stabbed the police officer.
Around three shots were heard.
Amid shouts and screams, two people were seen receiving treatment in New Palace Yard.
Armed police cleared the area, while paramedics rushed to help the injured.
Prime Minister Theresa May was confirmed as "OK" by a Downing Street source.
Locked in the Commons Chamber but my heart goes out to the police officers, those hit by the car on the bridge and their families. Stay safe
— David Lammy (@DavidLammy) March 22, 2017
Christian and Labour MP David Lammy took to Twitter to say: "Locked in the Commons Chamber but my heart goes out to the police officers, those hit by the car on the bridge and their families. Stay safe."
Christian and former education secretary Nicky Morgan: "The Division Bell had just gone and MPs were making their way to the House of Commons chamber. I was walking from Portcullis House along the path of Old Palace Yard when suddenly shots rang out.
"It takes a moment to realise that is actually gunfire and at that point people were yelling get down get back.
"They pushed us all back to the new building.
"We have at the back of our mind all the time that something terrible can happen. The first thing is is that actually gunfire? Have you misheard? But the reaction of the officers around made it very clear this is a very serious situation."
Click here to listen to Premier's Marcus Jones speaking with MP David Burrowes: