Islamic State Claims Responsibility for London Attack

Islamic State was responsible for an attack outside Britain's parliament that left four people dead, the group's Amaq news agency said on Thursday.

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London Police have named the attacker as Khalid Mahsood.

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Emergency personnel tend to an injured person close to the Palace of Westminster, London, Wednesday, March 22, 2017. Credit: Yui Mok/PA via AP

"The perpetrator of the attacks yesterday in front of the British parliament in London is an Islamic State soldier and he carried out the operation in response to calls to target citizens of the coalition," the Amaq statement said. 

Islamic State, which has controlled parts of Iraq and Syria in recent years, has lost territory this year to local forces in those countries supported by a U.S.-led military coalition. 

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Police officers in forensics suits search the grass on Parliament Square gardens outside the Houses of Parliament in central London on March 23, 2017.Credit: JUSTIN TALLIS/AFP

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Britain's Prime Minister Theresa May speaks in the Houses of Parliament, Thursday March 23, 2017Credit: PA/AP

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Members of Parliament stand for a minute's silence the morning after an attack in Westminster, London Britain, March 23, 2017.Credit: HANDOUT/REUTERS

Earlier on Thursday, British Prime Minister Theresa May told the House of Commons that the London attacker was British-born and earlier investigated by MI5 for links to violent extremism.

May says police believe the man acted alone and there is no reason to believe "imminent further attacks" are planned.

Police arrested seven people as part of an investigation into the lone-wolf attacker who killed three people and injured 40 before being shot dead by police near parliament in London on Wednesday, Britain's most senior counter-terrorism officer said.