Emergency services at the scene outside the Palace of Westminster, London, after policeman has been stabbed and his apparent attacker shot by officers in a major security incident at the Houses of Parliament. (PA)

Pictures have emerged of the man believed to be the suspect in a terror attack on the Houses of Parliament.

He allegedly rammed a car into members of the public on Westminster Bridge before entering the grounds of the Houses of Parliament and stabbing a police officer before he was shot.

Eyewitnesses described scenes of terror when gunfire rang out as the attacker approached a second officer within yards of the Houses of Parliament.

Pictures show two knives lying on the floor near the man, who appears to be dressed in black.

Two knives, circled in red, lay on the floor near the suspect (PA wire)

Armed officers are also seen standing nearby as he is treated by paramedics.

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

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 Tobias Ellwood among those who rushed to help.

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."

He added: "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."

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