British police conducted an anti-terror operation in north-west London and Kent overnight Thursday, the BBC reported.
During the operation, a woman was shot by police and four people were arrested. Officers said the operation was not connected to the earlier arrest of a man near Parliament.
The woman in her 20s was one of the subjects of the investigation and remains under police guard at hospital, according to the BBC.
Two men, aged 20 and 16 and a woman, 20, were arrested after the shooting. A 43-year-old woman was held in Kent.
The Metropolitan Police said they were arrested on suspicion of the commission, preparation and instigation of terrorist acts.
A police spokesman said searches at the locations of the arrests are ongoing, as well as further searches at linked addresses in London.
Earlier on Thursday, an armed terrorist on his way to an attack in London was nabbed just outside of Parliament.
The incident came a month after a terrorist, Khalid Masood, attacked pedestrians in Westminster, running down several with a rented SUV before stabbing several others. The attack left five dead and nearly 50 injured.