A 17-year-old boy was arrested on suspicion of murder and attempted murder over the stabbing which took place during the Taylor Swift-themed school holiday event in Southport, a seaside town near Liverpool, Merseyside Police said on Monday.

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 – in the latest headline-grabbing attack amid a recent rise in knife crime that has stoked anxieties and led to calls for the government to do more to clamp down on bladed weapons.

Two wounded adults who tried to shield the pupils were also in critical condition, police said.

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

The Taylor Swift-themed workshop was held during the first week of school holidays for children aged about six to 11.

The two-hour session was led by two women – a yoga instructor and a dance instructor – according to an online listing.

Witnesses described hearing blood-curdling screams and seeing children covered in blood emerging from the community centre that hosts everything from pregnancy workshops and meditation sessions to women’s bootcamps.

“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 the neck, back and chest.

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

King Charles III sent his “condolences, prayers and deepest sympathies” for those affected by the “utterly horrific incident”.

Police were called shortly before noon to a street where several small businesses are located behind rows of brick houses in the city of about 100,000.

The first officers who arrived were shocked to find so many casualties from the “ferocious attack”, most of them children with 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 eight kilometres from the site of the attack.

Mass shootings and killings with firearms are rare in Britain, where knives were used in about 40 per cent of homicides in the year to March 2023.