A London bus driver has described scenes of "panic" as a suspected terror attack unfolded outside the Houses of Parliament.

Michael Adamou was turning over Westminster Bridge when he saw what initially looked like an accident.

"In the beginning I thought maybe he lost control but then I heard shouting and screaming," he told The Independent.

"I saw people rushing into Parliament and the police were going crazy trying to stop everyone.

"A couple of seconds later I heard gunshots and then once the traffic started moving I could see the rest of the damage that he had caused - all the people laying on the floor."

The 25-year-old said up to 20 injured people were lying on the bridge, with two not moving.

Scotland Yard has confirmed five people died in the incident, including the attacker, a police officer and three others.

In pictures: Westminster attack Show all 9 1 /9 In pictures: Westminster attack In pictures: Westminster attack An air ambulance lands after gunfire sounds were heard close to the Palace of Westminster in London PA wire In pictures: Westminster attack MPs wait until the situation is under control in Westminster. 'The alleged assailant was shot by armed police,' David Lidington, leader of the House of Commons, told the house. BBC News In pictures: Westminster attack Crowds gather in Westminster after shooting incident, which police are treating as terror attack BBC News In pictures: Westminster attack Police were also called to an incident on Westminster Bridge nearby AP In pictures: Westminster attack Early reports indicate the car, which mounted the pavement on Westminster Bridge and mowed into around a dozen people, was the same vehicle which then rammed into the railings of the Palace of Westminster, just around the corner Reuters In pictures: Westminster attack Security sources described the suspected assailant as a middle-aged Asian man, who is understood to have left the car before attacking a police officer with a seven-to-eight inch knife PA wire In pictures: Westminster attack Police have asked people to avoid the immediate area to allow emergency services to deal with the ongoing incident AP In pictures: Westminster attack One woman has died and a number of others, including the police officer, have been hurt, according to a junior doctor at St Thomas' Hospital Reuters In pictures: Westminster attack At least three gun shots were heard by those inside Westminster, and proceedings in the House of Commons have been suspended AP

Police say at least 40 are injured, with dozens of ambulances and the London air ambulance evacuating casualties from the scene.

Mr Adamou said his passengers were "panicking" and trying to get off the trapped bus.

"After hearing gunshots I thought maybe a bomb was about to go off," he added.

"Once I got everyone off the bus I heard someone shouting that his wife had jumped into the river to avoid getting knocked over."

A woman has been pulled alive from the River Thames and was taken for medical treatment.

Witnesses told The Independent the car was left crashed into a wall next to the entrance to the Houses of Parliament.

Westminster attack update: How the day unfolded

A man believed to be the attacker was seen lying motionless a short distance from the vehicle on the floor. He was later seen being wheeled away by paramedics and has now been confirmed dead.

The attack is bring treated as a terrorist incident by police, following a series of Isis inspired attacks using vehicles and knives across Europe.

No group has yet claimed responsibility.

"In the beginning it looked like an accident, I was hoping it was an accident," Mr Adamou said.