At least 19 people have been confirmed killed in a suspected terror attack in Manchester Arena, late on Monday night, with over 50 wounded and the football world has begun to mourn the tragic loss of life.
Prime Minister Theresa May said the incident was being treated as a terrorist attack.
White House officials said President Trump, who was in Jerusalem at the time, was briefed on the bombing.
Police said they responded to reports of an explosion shortly after 10.35pm at the arena, which has a capacity for 21,000 people, and where the USA singer had been performing to an audience that included many children.
Greater Manchester Police chief Ian Hopkins told reporters that investigators were "working closely with the national counter terrorism policing network and United Kingdom intelligence partners".
"This is clearly a very concerning time for everyone", he said at a brief news conference early Tuesday.
"Everyone was running, looking for their children", Zach Bruce said via Twitter.
The crowd was made up of mainly younger people who had come to see Grande, who is on a European and Latin American tour.
Some of the concert-goers uploaded videos to the social networks showing people fleeing the area and screaming after the blasts. A representative said the singer was not injured.
Manchester Victoria station has been evacuated and trains are unable to run.
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Toronto Mayor John Tory said the city stands in solidarity with the people of Manchester while Ontario Premier Kathleen Wynne also said in a tweet that she is "horrified" by the loss of life in the British city. "You don't know if she's dead or alive and I don't know how people can do this to innocent children".
Gary Walker from Leeds told BBC Radio 5 Live he was hit by shrapnel in his foot and his wife sustained a stomach wound as they waited for their daughters.
Chris Pawley told 9NEWS he had left the concert when he "heard the biggest explosion ever".
A number of Manchester taxi services say they are offering free rides to people trapped by the incident.
The government is urging USA citizens in Manchester to heed directions from local authorities and be vigilant about their security.
Meanwhile, Taylor Swift said that she sent her "thoughts, prayers and tears" to those affected by the tragedy.
Another concertgoer, Sasina Akhtar, told The Manchester Evening News that the explosion ignited at the back of the arena after the last song. "Our hearts go out to all affected and to our city's emergency services".
Grande's role as Cat Valentine on Nickelodeon's high school sitcom "Victorious" propelled her to teen idol status, starting in 2010.
The Dangerous Woman tour is the third concert tour by 23-year-old Grande and supports her third studio album, "Dangerous Woman".