British police have said raids carried out in London and Kent "contained" a terror plot. In a separate incident hours earlier, police arrested a man under surveillance carrying knives near parliament.
British counter-terrorism police said Friday they had disrupted an active plot in raids in London and southeastern England.
Armed police firing tear gas raided a location in London and another in Kent on Thursday evening, arresting six suspects, Neil Basu, Senior National Coordinator for Counter Terrorism Policing, told reporters.
"An armed entry was necessary due to the nature of the intelligence that we were dealing with," said Basu, adding that the property had been under observation as part of an investigation.
One woman in her 20s was shot and seriously wounded in the London operation. She is under police supervision at a hospital but has not been arrested. Searches of three locations in London are ongoing.
Basu said that with the arrests all threats posed by the plot had been "contained." Those arrested are being question but have not been charged yet.
The raids capped an intense day for security forces, after a 27-year-old man under police surveillance was earlier arrested in a stop-and-search near Parliament and Downing Street allegedly carrying a bag of knives.
The man remains in custody for terrorism related offenses and possession of weapons, Basu said. Two addresses in London are also being searched in that investigation.
A 27-year-old bearded man wearing all black was arrested in Westminster only hours before raids targeted a separate suspected terror plot.
The Thursday evening raids and incident in Westminster were separate and unrelated, Basu said.
British authorities have been on high-alert for terrorism threats. Counter-terrorism officials have warned of al-Qaeda and the so-called "Islamic State" radicalizing British citizens and that returning jihadists from Syria and Iraq may strike at home.
Basu said security forces are constantly monitoring threats and "are making arrests on a near daily basis." There is also "a huge amount of unseen work that the public will never know about from us and our brilliant security services," he added.
The incident in Westminster stoked memories of a March 22 attack, in which a British-born Muslim convert mowed down pedestrians with a car on Westminster Bridge, killing four people, then stabbing and killing a police officer on the grounds of parliament. The man, Khalid Masood, was shot dead.