The security measures in London are being reviewed following Monday night’s deadly attack in Manchester, with more police officers to be deployed on the city’s streets, Mayor of London Sadiq Khan said Tuesday.

The London mayor expressed condolences to the victims and their families, calling the attack “barbaric” and “sickening.”

The blast, which the police are considering a terrorist attack at the moment, took place outside the Manchester Arena, at the end of US singer Ariana Grande’s concert, and left at least 22 people dead and almost 60 injured.

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