The man who mowed down pedestrians and stabbed a policeman in an assault on the heart of British democracy was 52-year-old Khalid Masood, who was born in Kent in southeast England, police said on Thursday.
He said there was a mix of nationalities among the dead but gave no details. The victims were a policeman who was stabbed and two members of the public, a woman in her mid-40s and a man in his mid-50s.
The fourth dead was the assailant.
The attack on Wednesday started when the assailant sped across Westminster Bridge in a car, ramming pedestrians along the way. He then ran towards parliament and stabbed the policeman before he was shot.
Three French high-school students aged 15 or 16, who were on a school trip to London with fellow students from Brittany, were among the injured.
French Foreign Minister Jean-Marc Ayrault was expected to arrive in London to visit them at hospital, French media reported.
Westminster Bridge remained cordoned off with a strong police presence. The nearby Westminster underground train station, normally a busy hub in the morning rush hour, was not accessible from street level as it was within the cordon.
Parliament was due to convene later in what Prime Minister Theresa May said late on Wednesday was a sign that the attack would not disrupt British democracy or normal life in the capital.