Seven arrests have been made in raids following the Westminster attack that left five dead, police have said.
Acting Deputy Commissioner and Head of Counter Terrorism Mark Rowley said hundreds of detectives have worked through the night, carrying out searches at six addresses.
The victims were a mix of nationalities, and included a woman in her 40s and a man in his 50s, he added.
Seven of the injured are still in hospital in a critical condition.
In the attack on Wednesday, a man drove a car along a pavement in Westminster knocking down pedestrians, leaving dozens injured.
He then stabbed a policeman and was shot dead by police in the grounds of Parliament.