Transcript for Security ramped up in Manchester for the Ariana Grande benefit concert

Back now as we continue to monitor that major police activity reported at the London bridge. Those details still coming in. Arianna Grandy sua grande surprising fans injured in the M booing in Manchester nearly two weeks ago. Safety precautions tight. This as police announced a 17th arrest in that case. ABC's lama Hasan with more. Reporter: Tonight, security ramping up in Manchester as Ariana grande prepares to take the stage for a benefit concert just 13 days after that devastating suicide attack. We were shocked and we just want to show our support. Reporter: Authorities are launching a massive security operation around the city of Manchester, creating a ring of steel to protect the 130,000 people not only going to the concert here, but also to the soccer game nearby. Barriers already in place and the police presence, expected to double. Officers pouring in from across the uk. I can understand some nervousness from members of the public, perhaps, but I can reassure them that come Sunday, they will see a heightened police presence. Reporter: Sisters Yasmin and Nadia were at the concert the night of the attack. Fighting fear with strength and defiance. Go into this tomorrow with all the love and the celebrities that are surrounding it and having in memories will have closure on the whole thing. Reporter: Grande paying an emotional visit to many of those injured in the attack, including one of the youngest, 8-year-old lily Harrison. I think the last sort of checkpoint for lily being discharged from the hospital was the psychological angle, and I think after last night, I think Ariana grande, as surreal as that sounds, got her over the edge. Reporter: Lily's father hopes she'll be out of the hospital and at the concert tomorrow. Concert that's providing a small glimmer of hope as word reaches here of yet another devastating attack in London. Tom? Lama Hasan for us tonight. Thank you so much. And the one love Manchester concert will be shown live on the channel freeform tomorrow at 2:00 P.M. Eastern. And later tomorrow night on ABC after the NBA finals.

This transcript has been automatically generated and may not be 100% accurate.