MANCHESTER TERROR ATTACK - WHAT WE KNOW SO FAR:
WHAT HAPPENED?
* A blast sparked a frantic evacuation of a concert hall in Manchester where US singer Ariana Grande was performing.
* The blast occurred on the anniversary of the murder of soldier Lee Rigby, who was hacked to death on a London street on May 22, 2013.
WHERE?
* The explosion occurred in the foyer of Manchester Arena at the end of the concert at around 10.30pm on Monday night local time.
* The venue is the largest indoor arena in Europe with the capacity to hold 21,000 people and has more than one million visitors every year.
* It opened in 1995 and has hosted A-list names including the Rolling Stones, Madonna, Pavarotti and Lady Gaga.
* The arena has also hosted sporting events such as the 2008 FINA World Swimming Championships and boxing matches featuring stars like Mike Tyson and David Haye.
HOW MANY HURT?
* British police have confirmed up to 22 people are dead and around 59 are injured.
* A total of 60 ambulances attended the incident.
WHAT ARE THE AUTHORITIES DOING?
* Police are treating the blast as a terrorist incident.
* No militant group has claimed responsibility so far but Islamic State supporters celebrated on social media.
* Police carried out a controlled explosion of a suspicious object that turned out to be abandoned clothing in a nearby park.
WHAT HAS THE BRITISH PM SAID?
* Prime Minister Theresa May said authorities were working to establish the full details of what police were treating as "an appalling terrorist attack".
* PM May's ruling Conservative Party, which has a big lead in opinion polls, is preparing to suspend election campaigning because of the blast.
WHAT HAVE WITNESSES SAID?
* "It was a huge explosion -- you could feel it in your chest. It was chaotic. Everybody was running and screaming and just trying to get out," concertgoer Catherine Macfarlane told Reuters.
* "Everyone just fled. Some people were injured. We saw blood on people when we got outside. People were just running all over the place," witness David Richardson told Manchester Evening News.
