IS terrorist group claimed responsibility for London terror attack killing four people and injuring 40 others on the Westminster Bridge and outside the UK Parliament, according to the terrorist group's affiliated Amaq News Agency.

Axar.az reports that, "The perpetrator of yesterday's attack in front of the British parliament was a soldier of the Islamic State and the operation was carried out in response to calls to target coalition countries," Amaq said citing a "security source."

It added that the person "carried out the operation in response to calls for targeting citizens of the coalition."

A knife-wielding man went on a deadly rampage in the heart of Britain's seat of power Wednesday, plowing a car into pedestrians on London's Westminster Bridge before stabbing a police officer to death inside the gates of Parliament. Four people were killed, including the assailant, and 40 others were injured in the London terror attack.

Lawmakers, lords, staff and visitors were locked down after the man was shot by police within the perimeter of Parliament, just yards (meters) from entrances to the building itself and in the shadow of the iconic Big Ben clock tower. The attacker died, as did three pedestrians on the bridge, and the police officer.