SOUTH Dorset MP Richard Drax has told he is among the MPs on 'lockdown' in the Houses of Parliament after shock attacks in Westminster which has left at least four dead and 20 others injured.

Two of the dead include a policeman who was stabbed at the Houses of Parliament and his attacker who was shot by officers.

The attacker mowed down several pedestrians, killing at least one woman, as he drove a grey Hyundai i40 across Westminster Bridge before crashing it into railings then running through the gates of the Palace of Westminster and stabbing the officer.

Eyewitnesses said he was shot by police as he approached a second officer clutching his knife.

Paramedics fought to save his life and that of his victim on the floor of the cobbled courtyard in front of Parliament with Foreign Office minister and Bournemouth East MP Tobias Ellwood among those who rushed to help.

Mr Ellwood, a former soldier, pictured below, gave CPR and mouth to mouth to the officer, and after trying to staunch the officer's wounds, he remained with the victim while the air ambulance arrived on the scene, landing in Parliament Square.

Dorset Echo:

The attacker left a trail of destruction as paramedics tended to his victims on the bridge and at the gate.

One woman died and a number of others were injured - including some with "catastrophic" injuries - in the incident on Westminster Bridge, a junior doctor at St Thomas' Hospital has reportedly said.  

Around three shots rang out outside the Palace of Westminster after a man ran through the gates into the front yard of the parliamentary compound apparently waving a knife.

Two people were seen being treated on the ground in New Palace Yard amid shouts and screams.

Dorset Echo:

Mr Drax said MPs were voting in the divisional lobby of the House when business was suspended and an announcement made.

He said: "We don't know much except reports that a policeman has been stabbed outside by someone who got into the front of Parliament.

"We are in lockdown and I understand people elsewhere on the Parliamentary estate have been told to stay inside for the timebeing.

"I also understand a car has mowed down people on Westminster Bridge.

"We are short on fact but the information and rumours reaching us are not good."

Mr Drax paid tribute to the work of the police, saying: "It underlines the job the police do and we are extremely grateful for the work they do. We are indebted to them. They are exceptionally brave."

Dorset Echo:

As the sitting in the House of Commons was suspended, Commons Leader David Lidington told MPs: "What I am able to say to the House is there has been a serious incident within the estate.

"It seems that a police officer has been stabbed, that the alleged assailant was shot by armed police.

"An air ambulance is currently attending the scene to remove the casualties.

"There are also reports of further violent incidents in the vicinity of the Palace of Westminster but I hope colleagues on all sides will appreciate that it'd be wrong of me to go into further details until we have confirmation from the police and from the House security authorities about what is going on."

Radoslaw Sikorski posted a video to Twitter purporting to show people lying injured in the road on Westminster Bridge.

Mr Sikorski, a senior fellow at Harvard Centre for European Studies, said he saw at least five people lying on the ground after being "mown down" by a car.

Prime Minister Theresa May was seen being ushered into a silver Jaguar in the grounds of the palace as what sounded like gunfire rang out at around 2.45pm.

A Downing Street source confirmed she was "OK".

Eyewitness Rick Longley described the attack.

"We were just walking up to the station and there was a loud bang and a guy, someone, crashed a car and took some pedestrians out.

"They were just laying there and then the whole crowd just surged around the corner by the gates just opposite Big Ben.

"A guy came past my right shoulder with a big knife and just started plunging it into the policeman.

"I have never seen anything like that. I just can't believe what I just saw."

A counter-terrorism investigation is already under way, police said.

Giving a statement outside Scotland Yard, police spokesman Commander BJ Harrington said: "A senior national coordinator has declared this a terrorist incident.

"Although we remain open-minded to the motive, a counter-terrorism investigation is already under way led by the Met counter-terrorism command.

"We received a number of different reports which included a body in the river, a car in collision with pedestrians and a man armed with a knife.

"Officers were already in the location as part of routine policing but immediately additional officers were sent."

He added: "I would 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 Victoria Embankment up to Embankment Tube station.

"This is to allow emergency services to deal with this ongoing incident.

"There is an ongoing investigation being led by the counter-terrorism command.

"We would ask anybody who has images or film of the incident to pass those to the police.

"We know there are a number casualties including police officers but at this stage we can not confirm numbers or the nature of these injuries."