A large crowd of anti-Muslim protesters has clashed with police in a northern English town where three girls were stabbed to death and five other children critically wounded at a dance event.

Police said they were supporters of the English Defence League which has previously staged violent demonstrations against Islam.

The police have not given any details about the 17-year-old male suspect, beyond saying he was born in Britain, but hundreds of people gathered in the town on Tuesday.

The suspect is in police custody on suspicion of murder and attempted murder after the incident at the “Taylor Swift yoga and dance workshop” in Southport, north of Liverpool, a summer holiday activity event for children aged from six to 11.

Police vehicles were damaged and set alight, and items were thrown towards a nearby mosque. One video posted online showed the crowd chanting “we want our country back”.

Assistant Chief Constable Alex Goss said the situation was unacceptable.

“”Yesterday, our officers and other members of the emergency services were faced with one of the most difficult situations they will ever face,” he said.

“Tonight, they find themselves being attacked as they endeavour to prevent disorder.”

Witnesses to the attack on Monday described what they saw as being like a scene from a horror film.

Eight other children suffered stab wounds and five remained in a critical condition. Two adults were also critically wounded attempting to protect the young victims, police said.

British Prime Minister Keir Starmer visited the town earlier on Tuesday, King Charles and his family expressed their shock, and interior minister Yvette Cooper told parliament that people must not speculate about the motive of the attack.

US pop star Swift wrote on Instagram that she was “just completely in shock”.

“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.”

Her fans have raised more than Stg125,000 ($A244,648) online to help families of the victims and for the hospital where some of the children were being treated.

The three girls who died in the attack were named as Bebe King, aged six, seven-year-old Elsie Dot Stancombe, and Alice Dasilva Aguiar, aged nine.

“Keep smiling and dancing like you love to do our Princess, like we said before to you, you’re always our princess and no one would change that. Love from Your Hero Daddy and Mummy,” Aguiar’s family said in a statement.

Merseyside Police said the motive was unclear but said they were not looking for anyone else in connection with the stabbings, amid fevered speculation on social media about the suspect, who was born in Cardiff and lived in a nearby village.

“We have already said that the person arrested was born in the UK and speculation helps nobody at this time,” Goss said.

The attack has shocked Southport, a quiet seaside town, and the country as a whole. Starmer paid a sombre visit to the scene on Tuesday to lay flowers and to meet police and paramedics who responded to the incident.