Her manager Scooter Braun issued a statement following the incident, saying "our hearts are broken" by the tragedy.
broken.— Ariana Grande (@ArianaGrande) May 23, 2017
from the bottom of my heart, i am so so sorry. i don't have words.
Ariana Grande has indefinitely postponed her world tour following a suicide bomb blast that killed 22 people at her concert in Manchester.
The 23-year-old singer has reportedly pulled out of her next concert, in London on Thursday, and is currently planning to reschedule the rest of her European shows.
According to TMZ, Ariana will put gigs in the UK, Belgium, Poland, Germany and Switzerland on hold, though no official announcement has yet been made.
Sources told the website the 'Problem' singer is "in hysterics" and incapable of performing right now and she and her team are "deeply concerned" about security.
Hours after the tragedy, Ariana took to Twitter to say she had been left "broken" by the incident.
Scooter said on the micro-blogging website: "Words cannot express our sorrow for the victims and families harmed in this senseless attack.
"We mourn the lives of children and loved ones taken by this cowardly act.
"We are thankful for the selfless service tonight of Manchester's first responders who rushed towards danger to help save lives.
"We ask all of you to hold the victims, their families, and all those affected in your hearts and prayers."
Meanwhile, the Manchester Arena - which has a capacity of 21,000 - is supposed to stage three gigs by Take That later this week.
Following the incident, UK Prime Minister Theresa May paid tribute to the victims and families of those involved in the attack, which she confirmed is "being treated by the police as an appalling terrorist attack".