London. A teenage boy with a knife attacked a children’s dance and yoga class in northwest England on Monday, killing two children and wounding 11 other people in a “ferocious” rampage that sent bloodied children running into a street to escape the horror, police and witnesses said.

A 17-year-old boy was arrested on suspicion of murder and attempted murder in the attack in Southport, a seaside town near Liverpool, Merseyside Police said. The motive was not clear, but police said detectives were not treating the attack as terror-related.

Nine children were wounded, six of them in critical condition. Two wounded adults who tried to protect them also were in critical condition, police said.

“We believe the adults who were injured were bravely trying to protect the children who were being attacked,” Police Chief Constable Serena Kennedy said.

The Taylor Swift-themed workshop was held on the first week of school vacation for children aged about 6 to 11. An advertisement for the two-hour session promised yoga, dance and bracelet-making.

Witnesses described hearing blood-curdling screams and seeing children covered in blood.

“They were in the road, running from the nursery,” said Bare Varathan, who owns a shop nearby. “They had been stabbed, here, here, here, everywhere,” indicating neck, back and chest.

Prime Minister Keir Starmer called the attack “horrendous and deeply shocking.”

Merseyside Police said officers were called at about noon to an address in Southport, a seaside town of about 100,000 people near Liverpool. It called it a “major incident” but said there was no wider threat to the public.

“When they arrived they were shocked to find that multiple people, many of whom were children, had been subjected to a ferocious attack and had suffered serious injuries,” Kennedy said.

Colin Parry, an auto body shop owner, said most of the stabbing victims appeared to be young girls.

“The mothers are coming here now and screaming," Parry said. “It is like a scene from a horror movie. ... It’s like something from America, not like sunny Southport.”

The suspect, who has not been identified, lived in a village about 5 miles (8 kilometers) from the site of the attack, police said. He was originally from Cardiff, Wales.

Ryan Carney, who lives with his mother in the street, said his mother saw emergency workers carrying children “covered in red, covered in blood. She said she could see the stab wounds in the backs of the children.”

“All this stuff never really happens around here,” he said. “You hear of it, stabbings and stuff like that in major cities, your Manchesters, your Londons. This is sunny Southport. That’s what people call it. The sun’s out. It’s a lovely place to be.”

Britain’s worst attack on children occurred in 1996, when 43-year-old Thomas Hamilton shot 16 kindergarten pupils and their teacher dead in a school gymnasium in Dunblane, Scotland. The UK subsequently banned the private ownership of almost all handguns.

Mass shootings and murders with firearms are rare in Britain, where knives were used in about 40 percent of homicides in the year to March 2023. Several headline-grabbing attacks and a recent rise in knife crime have stoked anxieties and led to calls for the government to do more to clamp down on bladed weapons.