So-called Islamic State have claimed they are behind the attack at an Ariana Grande concert at the Manchester Arena.
A suicide bomber detonated an explosive device and died in the blast in which at least 22 were killed and another 59 injured.
A the O2 arena in London has indicated that two Ariana Grande shows due to take place later this week may be cancelled or put off following the deadly attack on the singer's concert in Manchester.
A statement said they have been in contact with Grande's management and will be in contact with ticket holders as soon as they have further information.
It added that anyone visiting the venue in Greenwich, London, should allow extra time to go through enhanced security
Grande's team are considering the future of all remaining dates on her tour, according to ITV News Arts Editor Nina Nannar.
Singer Rihanna has said the suicide attack at a Ariana Grande pop concert "could have happened to any of us" as she offered her sympathies to the victims.
The singer said she was "devastated" to see a terror bombing targeting "innocent vulnerable kids".
A number of other pop stars and celebrities have also expressed their shock and paid tribute to the victims.
So-called Islamic State have claimed to be behind the terror attack at Manchester Arena which left 22 people dead and 59 injured.
The terror organisation claimed that the attack was carried out using an explosive device which was planted at the Ariana Grande concert.
In a translated statement the group said: "The destruction of 100 crusaders with an explosive IED in the city of Manchester, Britain.
"By the grace of god in revenge for the religion of god most high and the terrorism of the polytheists, as a response to their enmity and the lands of the Muslim, one of the soldiers of the caliphate has managed to place an IED in a group of crusaders in the city of Manchester Britain.
"And it was in the building of the arena of the party which results in the death of 30 crusaders and injury of 70 others."
The head of Britain's internal security services has said they are working "relentlessly" to keep the country safe.
Andrew Parker, the director general of MI5, said the Manchester terror attack was "disgusting" in a statement.
The Queen has said the whole nation has been shocked by the suicide bomb attack at Manchester Arena.
In a statement offering her deepest sympathy to those affected, she also expressed her admiration for the way the people of Manchester have shown "humanity and compassion" in response to the "act of barbarity".
At least 12 of the victims of the Manchester Arena terror attack are children.
Not much detail has been released about the conditions of the injured but a North West Ambulance Service confirmed a dozen youngsters were taken to Manchester Children's Hospital.
In total 59 people were injured and 22 have been confirmed dead.
