British police said officers shot a woman and arrested four other people in London and nearby Kent during a counter-terrorism investigation on Thursday.

The woman in her twenties was shot at an address in north-west London, police said. She has not been arrested yet and is under police guard at the hospital, according to the statement.

The evening raid saw three people arrested on terrorism charges, including two at the scene -- a 16-year-old boy and a 20-year-old woman -- as well as a 20-year-old man nearby.

Police also arrested a 43-year-old woman in Kent, south-east England, following the London raid.

Police did not release the names of the five people, who the police said had been under observation by counter-terrorism officers as part of an ongoing intelligence led operation.

All five people were arrested on suspicion of the commission, preparation and instigation of terrorist acts, metropolitan police said in a statement, adding that the incident was not connected to the arrest in Whitehall, where a man carrying knives near Prime Minister Theresa May's office was arrested on suspicion of preparing an act of terrorism.