New York - The explosion that went off at the Ariana Grande concert is the deadliest attack in Britain since 2005.
Police said at least 22 people were killed and around 59 were wounded in the attack just as Grande left the stage.
British Prime Minister Theresa May says the government is working to learn the full details of the blast.
May says the government is trying to establish "the full details of what is being treated by the police as an appalling terrorist attack."
New York authorities on Monday stepped up security at sensitive sites after a deadly blast at a concert in Britain, although officials said there was no indication of a threat to US targets.
New York Governor Andrew Cuomo said he was ordering additional patrols at "high-profile locations" including airports and the subway "out of an abundance of caution" after the assault at the show by US pop star Ariana Grande.
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