Westminster station, which faces parliament, was evacuated
The account has posted a step-by-step diagram describing the brutal attacks which unfolded in the capital city.
At least two people are dead and more are suffering from “catastrophic injuries”, medics at St Thomas’ hospital have reported.
While ISIS has not claimed responsibility for the attacks, Ahmet Yayla, professor of Criminology and Former Counterterrorism Police Chief in Turkey, is relaying updates from ISIS’ telegram, an encrypted messaging service.
Mr Yayla has reported the ISIS account is: “Cheering for the #Westminster #Westmattack and posted the scheme for the attack. #London #ISIS.”
— Ahmet S Yayla (@ahmetsyayla) March 22, 2017
He added: “This is the same account that posted the Istanbul #Reinaclub attack video.
“However, there are no official claims of the #Westminster attack.”
The Met Police have called the shocking events a terror attack.
So far two people have been confirmed dead, and a statement issued by officers said: “We know there are number of casualties including police officers but cannot confirm number or nature of injures.”
A car ploughed into 12 pedestrians on Westminster bridge just before 3pm on Wednesday afternoon, before carrying on to parliament where it is thought more people were injured as the car crashed into the perimeter fence.
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A knifeman, thought to be the driver or passenger, made their way into Old Palace Yard before attacking a police officer.
They were then shot by armed officers.
Parliament was put into lockdown and business suspended. MPs are still thought to be inside the Thames front building.
Westminster station, which faces parliament, was evacuated and the police have warned people to stay away from key London landmarks such as Parliament Square and Whitehall.
London Terror Attack: LIVE PICTURES Wed, March 22, 2017
Two dead, 12 injured as knifeman mows into crowd in Westminster
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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