Police officers and forensic personnel stand behind a cordon on Hart Street in Southport, northwest England, following a knife attack. Photo: Darren Staples / AFP
By Gemma Sherlock, Monica Rimmer, Lauren Potts, and Kara O'Neill, BBC News, Merseyside
Two children have died and nine were injured, six of them critically, in a "ferocious" knife attack at a children's dance workshop.
Two adults are also in a critical condition after being stabbed as they tried to protect children at the Taylor Swift-themed event on Hart Street in Southport, Merseyside Police said.
A 17-year-old boy, from Banks in Lancashire, has been arrested on suspicion of murder and attempted murder.
Police said the motivation for the attack was "unclear" but it was not being treated as terror-related.
One witness described the scene as "horrendous" and said they had "never seen anything like it".
The King and the prime minister have led tributes to the victims, offering their "heartfelt condolences" to those affected.
Merseyside Police declared a major incident after receiving emergency calls at 11.47am local time, on what was the first full week of the school summer holidays for many children in the UK.
Armed response vehicles, 13 ambulances and the fire service rushed to the dance class, which was being held for children aged six to 10.
Chief Constable Serena Kennedy told a news conference that officers responding to the calls "were shocked" to find that multiple people, many of whom were children, had been subjected to a "ferocious attack" and had suffered serious injuries.
"It is understood that the children were attending a Taylor Swift event at a dance school when the offender armed with a knife walked into the premises and started to attack the children," she said.
"We believe that the adults who were injured were bravely trying to protect the children who were being attacked."
She added: "As a mum of two daughters, and the nana of a five-year-old granddaughter, I cannot begin to imagine the pain and suffering the families of the victims are currently going through and I want to send them our heartfelt condolences and sympathies".
Kennedy said the 17-year-old suspect, who police said was born in Cardiff, will now be questioned by detectives.
Merseyside Police said it was not looking for anyone else in connection with the attack and that the "motivation for the incident remains unclear".
Kennedy added that Counter Terrorism Police North West had offered their support to Merseyside Police but that the incident was not currently being treated as terror-related.
Journalist Tim Johnson, from Eye on Southport, said the attack happened at the Hope of Hart children's club, which is housed in a former warehouse building on a back street.
"It was horrendous. I've never seen anything like it," Johnson said.
"There were so many police cars, it was a mass of blue lights. I saw ambulance men and women in tears. People were in tears in the streets."
Alder Hey Children's Hospital declared a "major incident", while the North West Ambulance Service said it had sent 13 ambulances to the scene.
Dave Kitchin, head of operations at the ambulance service, said they treated 11 casualties at the scene, who were sent by emergency ambulance and heli-med to Alder Hey and Royal Manchester Children's hospitals, Aintree University Hospital, Southport and Formby District General Hospital and Ormskirk District General Hospital.
He described the scene that met paramedics as "devastating", adding, "no doubt this incident will have a lasting impact on the whole community, and our thoughts are very much with them at this difficult time".
Great North Air Ambulance Service confirmed its critical care team was also sent to the scene.
A spokesman added: "We delivered advanced emergency care to one patient before accompanying them to hospital by road."
A business owner who called the police said the attack was like a "scene in a horror movie".
Colin Parry, owner of Masters Vehicle Body Repairs on Hart Street, said he believed six or seven "young girls" had been stabbed.
"It's like something from America, not like sunny Southport," he said.
Parry told BBC Radio 5 Live that a builder helped lead some of the children away from the scene of the attack and neighbours helped take "about 10 girls to safety".
"The community was coming together, everyone was trying to help. Everyone was trying to save the young kids," he added.
Condolences flow
In a statement on X, The King said he and his wife were "profoundly shocked" to hear of the "utterly horrific incident".
He added: "We send our most heartfelt condolences, prayers and deepest sympathies to the families and loved ones of those who have so tragically lost their lives, and to all those affected by this truly appalling attack."
The Prince and Princess of Wales called the attack "horrid and heinous" adding that they were sending "love, thoughts and prayers to all those involved".
They said on X: "As parents, we cannot begin to imagine what the families, friends and loved ones of those killed and injured in Southport today are going through.
"Thank you also to the emergency responders who, despite being met with the most horrific scenes, demonstrated compassion and professionalism when your community needed you most."
Prime Minister Sir Keir Starmer said: "I know the whole country is deeply shocked about what they've seen and what they've heard.
"I know I speak for everyone in the whole country in saying, our thoughts and condolences are with the victims, their families, their friends and the wider community and it's almost impossible to imagine the grief that they're going through, and the trauma that they're going through.
"I do want to thank the emergency services and Merseyside Police who have had to respond to the most difficult of circumstances today."
Everton Football Club and Liverpool Football Club also offered their condolences to all those affected.
In a joint statement, both clubs said on X: "Everton and LFC football clubs come together to send our love and support to all those affected by today's tragic events in Southport. You are in our thoughts and prayers."
Home Secretary Yvette Cooper said she was "deeply concerned" about the "very serious incident", while Southport MP Patrick Hurley added that he was "hoping for the best possible outcomes to the casualties affected".
Steve Rotheram, mayor of Liverpool City Region, has urged the public not to spread "unconfirmed speculation and false information".
Merseyside's Police and Crime Commissioner Emily Spurrell said she was "utterly shocked and devastated" to hear of the "truly appalling" incident.
She said: "To hear that innocent, defenceless children have been attacked during a Taylor Swift event at a dance school as they enjoyed the start of the school summer holidays is unthinkable and absolutely abhorrent.
"These young people had their whole lives ahead of them and it is hard to find the words to convey our deep sadness".
Councillor Marion Atkinson, Leader of Sefton Council, said the council was "deeply shocked and saddened at the tragic events".
"Our thoughts are with all the victims of this attack and their families," she said.
"I'd like to thank all those who responded to the incident and helped in any way they could in what must have been extremely difficult circumstances.
"We know this has caused concern and upset in the local community and while there is no immediate threat to the public we will be providing help and support in the coming days and weeks".
- BBC - additional reporting by PA Media.