Two children have been killed and nine injured, six critically, in a "ferocious" knife attack at a children's dance workshop.
According to BBC report, 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 11.47 BST, 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.
