Ariana Grande’s manager has said the One Love Manchester concert will “go ahead with greater purpose” following the London attack.
Scooter Braun tweeted that “all artists involved have been unwavering in their support this morning and are determined to carry on with the show”.
Thousands of people are heading to the city for a tribute concert remembering the lives lost in the 22 May attack.
Police said there would be additional security in place.
Greater Manchester Police said it was “deeply saddened” about the events in London.
Assistant Chief Constable Garry Shewan said: “Our thoughts are with everyone affected, including the emergency services responding to the incident.”
He said the concert – and Michael Carrick’s testimonial at Old Trafford football ground – would still take place but “with additional security in place to ensure the safety of everyone”.
“There will be additional security checks taking place and everyone will be searched, including bags. We would ask people not to bring bags if they can, as this will help speed up entry,” Mr Shewan added.
Music fans who started queuing outside the ground hours before the concert said they had not been deterred by the events in London.
One fan, who had been at the ground since 08:30 BST, said: “I am a bit scared of course, I’m very aware of what’s going on around me.
“But it’s going to be an absolutely fantastic tribute from some amazing artists.”
Sophie Wheeler and Erin O’Connor, 17, said they felt “pretty safe coming, knowing that they’re not going to put anything on without us being in complete safety, especially with the events that have happened last night”.
“They shouldn’t really let the terrorists put you off from doing things that you want to do.”
Manchester City Council leader Sir Richard Leese sent his sympathy to those affected by the London attack and said: “The people of Manchester have shown incredible togetherness and resolve in the aftermath of the recent attack on our city and this, I’m sure, will be demonstrated once again at tonight’s One Love Manchester concert.
“While it is important that people remain vigilant, it is vital that we do not allow those who hate our way of life and our solidarity to prevail.”
The concert will raise money for those affected by the suicide bombing at the end of Ariana Grande’s performance at the Manchester Arena.
Twenty-two people were killed, including children and teenagers who saw the show as well as parents arriving at the arena to pick them up at the end of the night.
Grande said she wanted to return to the “incredibly brave city” to spend time with her fans and to “honour and raise money for the victims and their families”.
She will be joined by stars including Justin Bieber, Coldplay, Take That and Katy Perry.
The Old Trafford cricket ground has a 50,000 capacity and tickets sold out within 20 minutes when they went on general sale.
Some tickets were set aside for fans who attended the original concert.
Grande tweeted after the incident in the capital that she was “praying for London”.