Scotland Yard said three properties - two in Westminster and one in Barnet are being searched along with a number of cars - after two men were arrested on suspicion of terror offences.
Police said that one of the arrests in Westminster took place at a residential address and not near any major landmark.
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Finnish media say several people have been wounded in a stabbing in the city of Turku in western Finland.
Longer spells of rain across eastern Scotland with a weather warning in place until 6pm.
Julian Cadman, who is thought to have dual British-Australian nationality, became separated from his mother who was injured in the attack.