A 9-year-old girl has become the third child to die following a knife attack at a Taylor Swift-themed holiday club in the U.K.

Merseyside Police said the youngster died in the early hours of Tuesday morning following the deaths of two other girls, aged 6 and 7, in the attack in the northwestern English seaside town of Southport on Monday.

A 17-year-old boy, who cannot be named for legal reasons, remains in custody accused of murder and attempted murder following the incident at a dance studio.

Eight other children suffered stab wounds and five are in critical condition, alongside two adults who were critically injured, police said.

The fully booked club for children, which was advertised as a dance, bracelet-making and yoga workshop, quickly became something "like a horror movie," witnesses to the deadly stabbings have said.

U.S. singer Taylor Swift said she is "completely in shock" after the "horror" of the knife attack.

In a statement released on social media on Tuesday, Swift said: "The horror of yesterday’s attack in Southport is washing over me continuously, and I’m just completely in shock.

"The loss of life and innocence, and the horrendous trauma inflicted on everyone who was there, the families and the first responders.

"These were just little kids at a dance class. I am at a complete loss for how to ever convey my sympathies to these families."

Police said a name shared on social media in connection with the suspect is "incorrect," adding: "We would urge people not to speculate on details of the incident while the investigation is ongoing."

Tributes have been paid on social media to the bravery of dance and yoga teacher Leanne Lucas after she was attacked in the incident.

Lucas was named as an organizer of the event run by Southport-based business Enlighten in a post on Facebook.

British Home Secretary Yvette Cooper is expected to make a statement on the attacks later on Tuesday in the House of Commons, the lower house of parliament.

She earlier met first responders in the town and laid flowers at the police cordon.

Police have said that, although the motive for the attack is unclear, it is not believed to be terror-related.

At the scene, flowers and teddies have been left close to the police cordon.

Staff from Natterjacks Day Nursery laid flowers and a heart-shaped artwork decorated with children’s handprints.

A message on the artwork said: "The brightest stars are now dancing with the angels in heaven.

"Shine bright little ones, we will never forget your smiles and laughter."

People, including children, continued to arrive throughout the morning to lay tributes; some were in tears as they walked away.

One message in a "Thinking Of You" card said "thoughts and prayers" are with those affected and was signed "Love – Southport."

Another said: "Fly high with angels, little ones."

The Daily Telegraph newspaper reported that businessman Jonathan Hayes was stabbed in the leg after attempting to disarm the attacker.

His wife Helen told the newspaper: "Our office is in the same building as the dance studio. He heard screams and went outside, saw the attacker, saw that he had hurt a child and tried to take the knife off him and got stabbed in the leg."

She said she had been with her husband at the hospital all afternoon and added: "He’s very upset that he wasn’t able to be more help. Physically he will be OK, mentally I don’t know."

Witnesses to the incident said the alleged knifeman arrived at the dance studio in a taxi and got out without paying.

One person told the Daily Telegraph that the attacker wore a black hooded top and a face mask.

The witness said the suspect then walked into the studio through a front door that was unlocked for fire safety reasons.