As per AFP, Greater Manchester Police says that 22 people have died because of the attack already. The attacker died detonating the bomb, they said.
"This is currently being treated as a terrorist incident until police know otherwise," the statement said.
Eyewitnesses reported hearing a loud "bang" from inside the venue. Video footage from the scene showed bloodied victims being helped by emergency services.
Here is what we know so far:
—Labour leader Jeremy Corbyn and Liberal Democrat leader Tim Farron have also expressed their sympathies for the victims.
—Prime Minister Theresa May said the incident was being treated as a terrorist attack. She is set to chair an emergency Cobra meeting in response to the atrocity, reports Daily Star.
—Police have set up a helpline for people who are worried about loved ones on 0161 856 9400.
—Large areas around the arena have been sealed off and Victoria Station has been closed and is expected to be closed throughout Tuesday.
—UK police responded to reports of an explosion shortly after 10:33 pm (2133 GMT) at the arena, which has the capacity to hold 21,000 people, where the Ariane Grande had been performing to an audience that included many children, according to Reuters.
—The blasts reportedly went off at the end of the concert near the box office area of the venue. "It was one bang and essentially everyone from the other side of the arena where the bang was heard from suddenly came running towards us," an eyewitness said.
—22 people have been reported killed while 50 others are injured.
—The blast was reported to have hit the foyer of the building at 10:30pm.
—The attacker was killed trying to detonate the bomb
Facts about Manchester Attack
1. Britain's deadliest attack since 2005
According to Daily Star, if Monday's incident is confirmed as terror attack, it would be the deadliest militant assault in Britain since four British Muslims killed 52 people in suicide bombings on London's transport system in July 2005.
2. Lee Rigby's blood-curdling murder
The blast took place on the anniversary of a British Army soldier Lee Rigby, who was brutally killed by jihadists on May 22, 2013. He was attacked by Michael Adebolajo and Michael Adebowale (British of Nigerian descent) near the Royal Artillery Barracks in Woolwich, southeast London.
Rigby was off duty and walking along Wellington Street when he was attacked. Adebolajo and Adebowale ran him down with a car, then used knives and a cleaver to stab and hack him to death. The men dragged Rigby's body into the road and remained at the scene until police arrived. They told passers-by that they had killed a soldier to avenge the killing of Muslims by the British armed forces.
As soon as the blast took place at Ariana Grande's concert, her spokesperson confirmed that she was safe. However, the attack had a tremendous effect on her.
broken.
from the bottom of my heart, i am so so sorry. i don't have words.
— Ariana Grande (@ArianaGrande)
May 23, 2017
Some concert goes still missing:
Concert-goer whose photograph is being widely shared on social media is Olivia Campbell, a teenager who attended the concert as part of a birthday present for her friend, Adam, who is also missing.
Here are other people missing:
This is how Hollywood celebs reacted to the attack
Thoughts, prayers and my whole ?? are with Manchester this evening.
— Jennifer Lopez (@JLo)
May 23, 2017
My heart hurts for my sister, Ariana & every family affected by this tragic event in the U.K. Innocent lives lost. I'm so sorry to hear this
— NICKI MINAJ (@NICKIMINAJ)
May 23, 2017
No words can describe how I feel about what happened in Manchester. I don't wanna believe that the world we live in could be so cruel.
— Bruno Mars (@BrunoMars)
May 23, 2017
My thoughts and prayers are with the people of Manchester, any one affected, @ArianaGrande and the entire crew. Heartbreaking
— P!nk (@Pink)
May 23, 2017
This story is so sad and so scary. Sending all my love to Manchester.
— Ellen DeGeneres (@TheEllenShow)
May 23, 2017
My thoughts and prayers go out to everyone affected in Manchester.
— Selena Gomez (@selenagomez)
May 23, 2017
Sending love to the U.K., @ArianaGrande and all of her supporters who were caught up in this awful attack. Heartbreaking.
— John Legend (@johnlegend)
May 23, 2017
Tearing up imagining innocent concert goers losing their lives.. praying for everyone and all #arianators. ????????????????????????
— Demi Lovato (@ddlovato)
May 22, 2017
 "Manchester attack, ariana grande, ariana grande attack")
