A man has been arrested after an 11-year-old girl and a 34-year-old woman were stabbed in central London, according to the Metropolitan Police.
Monday's attack occurred in Leicester Square, a magnet for tourists with its shops, theatres and cinemas.
The square and surrounding area have an estimated 2.5 million visitors every week.
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Police said the two victims were taken to a major trauma centre. The extent of their injuries was not immediately clear.
The stabbing occurred as Britain is on edge after violence for the past week as crowds spouting anti-immigrant and Islamophobic slogans clashed with police.
The disturbances have been fuelled by right-wing activists who used social media to spread misinformation about a knife attack that killed three girls during a Taylor Swift-themed dance event.
It was not immediately clear whether the stabbing had any link to the unrest.
Police had been braced for further riots over the weekend, but no widespread unrest emerged.
Ministers remained on high alert, Prime Minister Keir Starmer's office said, adding its work was not done in dealing with the fallout from the violence.
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