London : A powerful blast ripped through a crowded arena hosting US star Ariana Grande's pop concert in the English city of Manchester, killing 19 people and injuring about 50 others, in one of the deadliest terror attacks in the UK.
Children and teenagers were feared among the dead because of the very young demographic of the pop star's fans, with desperate parents and relatives waiting for the news of loved ones after the blast struck the Manchester Arena last night.
"Police were called to reports of an explosion at Manchester Arena. So far 19 people have been confirmed dead with around 50 others injured. This is currently being treated as a terrorist incident until police know otherwise," Greater Manchester Police said in a statement.
Prime Minister Theresa May condemned the "appalling terrorist attack". She said her thoughts were with the victims and families of those affected in "what is being treated by the police as an appalling terrorist attack".
May said the government was working to establish the full details of the incident.
Unconfirmed reports from two unnamed US officials suggested the attack was carried out by a suicide bomber.
Pop star Grande's spokesperson said she was safe.
British Transport Police said the explosion occurred in the foyer area of Manchester Arena that has a capacity of 21,000.
Greater Manchester Police also carried out a "controlled explosion" in theCathedral Gardens area near the Manchester Arena, but have since confirmed the item they found was abandoned clothing and not dangerous.
Armed police lined the streets outside the arena with officers moving members of the public away and bomb disposal units at the site of the blast.
Reacting to the incident, Opposition Labour Party leader Jeremy Corbyn tweeted, "Terrible incident in Manchester. My thoughts are with all those affected and our brilliant emergency services."
Manchester Mayor Andy Burnham said, "My heart goes out to families who have lost loved ones, my admiration to our brave emergency services. A terrible night for our great city."
Eyewitnesses reported hearing a loud "bang" from inside the venue, which was playing host to the concert by Grande.
Video footage from the scene showed bloodied victims being helped by emergency services.
"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.
"Some people were screaming they'd seen blood but other people were saying it ballooned busting or a speaker had been popped," said another eyewitness.
The UK's Network Rail said train lines out of Manchester Victoria station, which is close to the concert venue, were blocked.
Manchester Arena is the biggest indoor venue in the city. The arena foyer connects with Victoria train and tram station, a major hub on the northern edge of the city centre.
The arena regularly hosts concerts by major stars like Grande -- a 23-year-old American TV teen actress-turned-pop star.
Grande is currently on a European tour -- she has already played in Birmingham and Dublin and is due to be at the O2 Arena in London tomorrow and Thursday.
Last night's blast came two months after a careening driver left four people dead on London's Westminster Bridge, then stabbed to death a police officer at the gates of Parliament.