Isis has claimed responsibility for the Westminster attack that left three victims dead in the heart of London.
A statement published by the group's Amaq propaganda agency said a "soldier of the Islamic State" had carried out the atrocity by the Houses of Parliament, The Independent reported.
It said the man was following a call made by the group to launch attacks on civilians and security forces in countries allied to the US-led coalition bombing its territories in Syria and Iraq.
The wording of the statement mentioned no direct involvement in the attack, which investigators have said was inspired by Islamist terrorism.
Isis frequently claims responsibility for terror attacks that it has not directly orchestrated or facilitated, but that are publicly linked to its ideology.
Metropolitan Police detectives are investigating the attack as terror-related but have not named any particular group.
Eight people have been arrested in a series of overnight arrests in London and Birmingham, where the attacker hired the car used in the massacre.
Aysha Frade was the second victim named following Wednesday’s atrocity, where PC Keith Palmer was stabbed to death outside the Houses of Parliament.
She and another member of the public, a man in his 50s, died of injuries sustained on Westminster Bridge as an attacker sped his car along the pavement.
He crashed it into gates next to the Houses of Parliament before getting out and bursting through the entrance, stabbing PC Palmer before being shot dead at around 2.40pm.
Theresa May said the attacker, who has not been officially named, was British-born and had been the subject of a historical investigation over violent extremism by MI5.