Six children and two adults remain in critical condition as police continue to question a 17-year-old boy over a deadly knife attack in Southport.

Two children were killed after a suspected teenage knifeman attacked a Taylor Swift-themed holiday dance class on Monday morning.

The boy, born in Cardiff, is being held on suspicion of murder and attempted murder following the attack in Hart Street, Southport, Merseyside Police said.

Further details of the victims, including age and gender, have not been given by police, who said they are not treating the incident as terror-related but added the motive “remains unclear”.

Three other children were injured in the stabbing while the two adults were hurt trying to protect the youngsters, the force said.

All the casualties are now being treated in hospitals, including children’s hospitals in Liverpool and Manchester.

The King said on Monday evening that he and the Queen had been “profoundly shocked” to hear of the “utterly horrific incident in Southport today”.

Southport incident
(left to right) Merseyside Head of Service Dave Kitchin, Merseyside Police Chief Constable Serena Kennedy, MFRS Chief Fire Officer Phil Garrigan and NWAS Cheshire, speaking to the media (James Speakman/PA)

Charles 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.”

And the Prince and Princess of Wales said: “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.

“We send our love, thoughts and prayers to all those involved in this horrid and heinous attack.

“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.”

Following a police press conference on Monday evening, the Prime Minister offered his condolences to the victims of the attack in Southport, and their families and friends, saying “the whole country is deeply shocked”.

The suspect is from Banks, a village outside Southport, and a road in the area was cordoned off by police on Monday afternoon.

Merseyside Police had declared a major incident at the scene in Southport, after receiving emergency calls at 11.50am on Monday, with armed response vehicles, 13 ambulances and the fire service descending on the scene, a school holiday club for children aged six to 11.

The children were attending a Taylor Swift event at the dance school when the attacker walked into the premises with a knife and began stabbing.

Southport incident
Emergency services near the scene in Hart Street, Southport (James Speakman/PA)

One local said one of the two adults injured in the attack locked herself in a room with children to protect them as eyewitnesses reported hearing screaming and seeing children “covered” in blood, suffering stab wounds.

Colin Parry, the owner of the Masters Vehicle Body Repairs 50 metres or so from the scene of the attack, told The Guardian he had a heated exchange with a young man he believed to be the attacker moments before the attack.

He said: “He came down our driveway in a taxi and didn’t pay for the taxi, so I confronted him at that point. He was quite aggressive he said: ‘What are you gonna do about it?’.”

Mr Parry said the man he now believes was the attacker then turned and walked out of the driveway of his business.

Southport incident
Locals watch on as ambulances and police attend the scene after two children were killed and six others were left critical after a knife attack in Southport. (James Speakman/PA)

Moments later, Mr Parry said he received a phone call from a colleague who had run to the dance studio after he heard “screaming that wasn’t normal”, he added.

Mr Parry said a member of staff saw “about 10 kids go running past him, all bleeding, and one of them collapsed on the floor outside the neighbour next door”.

“I went out and there’s two or three kids just lying on the floor. I mean, it’s a frenzied attack,” he said.

“It’s not one stab. He’s gone crazy, the lad’s gone crazy.”

The class was “fully booked” and “was attended by 25 youngsters and included a dance and yoga workshop plus bracelet making.

Social media posts advertising the event, which said the class was “open to children in Year 2 – Year 6”, have been inundated with comments in tribute to those who died and were injured.

One comment under the “Swiftie” event read: “Shocking, overwhelmed with grief. Deepest condolences to all effected by this senseless cruel act of violence against the innocent children and family’s. Prayers of strength to endure.”

Another said: “Can’t stop thinking about the tragic event that has happened today. Sending love to all affected .”

A third directed a comment at the teachers of the class, adding: “If you managed to get just one of those children out unharmed then you are a hero! Praying for your recovery and praying for all the children and families affected by this awful nightmare.”