A woman in her twenties has been shot by police and four people arrested during terror raids in London and Kent.
The injured suspect is being held under police guard after being rushed to hospital in a serious condition following the swoop at a north London address.
Police said she was a subject of an ongoing investigation by counter-terror officers who are searching several addresses across London.
The raids are not connected to an earlier incident when a man carrying knives was arrested near Downing Street on suspicion of planning a terror attack, Scotland Yard said.
The woman was shot as officers entered an address in Harlesden Road, Willesden, shortly before 7pm on Thursday.
Video posted online appeared to show heavily armed police clad in black storming a terraced house as loud bangs rang out.
One described seeing "loads of police with balaclavas, streets cordoned off, ambulances".
The Metropolitan Police said a 16-year-old boy and a 20-year-old woman were arrested at the property and a 20-year-old man was detained nearby.
A 43-year-old woman was arrested in Kent shortly after the raid and all four are being held on suspicion of the commission, preparation and instigation of terrorist acts at a south London police station.
The injured woman has not been arrested due to her condition, which police described as "serious but stable".
No other injuries have been reported.
Police said the property and people connected to it had been "under observation by counter-terrorism officers as part of an ongoing intelligence-led operation".
Further searches at linked addresses across London are under way, although the locations have not been disclosed.
The incident has been referred to the Metropolitan Police's Directorate of Professional Standards and the Independent Police Complaints Commission (IPCC) "as a matter of course", Scotland Yard said.
Police said the operation was unconnected to the earlier arrest of a 27-year-old man armed with knives in Westminster.
During an "intelligence-led" operation, terror police swooped on the suspect close to Downing Street and the scene of the deadly Westminster Bridge attack.