London, April 28 (IANS): Four persons were arrested and one injured during a counter terrorism operation in London and Kent in England, the Metropolitan Police said on Friday.

Officers said the operation on Thursday night was not related to an arrest earlier in the day in Westminster when a man was detained on suspicion of terror offences after being caught carrying several knives in his bag, Efe news reported.

During the operation, a woman in her 20s was shot by police officers after they entered a house on Harlesden Road in Willesden, northwest London.

The woman - whose identity and nationality were not disclosed - was taken to hospital and remains in serious but stable condition, the police said.

Two men, aged 20 and 16, and a woman, 20, were arrested in Willesden, while a woman, 43, was arrested in Kent.

Scotland Yard said that all have been arrested on suspicion of the commission, preparation and instigation of terrorist acts.

The man, 27, arrested near parliament on Thursday on suspicion of terror offences, remains detained "on suspicion of possession of an offensive weapon and on suspicion of the commission, preparation and instigation of acts of terrorism".