ISIS has claimed responsibility for Wednesday's deadly terrorist attack in London, according to multiple media reports that cite an Arabic-language statement from group called Amaq, an agency used to broadcast the terrorist organisation's propaganda.

U.K. Prime Minister Theresa May confirmed earlier Thursday that the attacker in Wednesday's deadly terror attack outside the Palace of Westminster was British-born and had previously been investigated for extremist behaviour by the country's security services.

"The attacker yesterday in front of the British parliament in London was a solider of the Islamic State, executing the operation in response to calls to target citizens of coalition nations," the statement said, according to an English translation. 

TST Recommends

Speaking to lawmakers during a special session of Parliament in the House of Commons -- only a few metres from where yesterday's deadly terrorist attack took place -- May described the alleged assailant as a "a peripheral figure" but repeated the Metropolitan Police's view that the "working assumption is that the attacker was inspired by Islamist ideology." May reiterated her stance that the business of government can and must continue.

The identity of the attacker is known to both the Met and MI5, Britain's security services, but has not been identified to the public. In an official statement outside New Scotland Yard HQ in London earlier Thursday, Acting Deputy Police Commissioner Mark Rowley said that six addresses around the country had been searched, including during an overnight raid on a house in Birmingham, and that eight arrests had been made.