A 17-year-old male, already in custody, has been charged with murder for the deaths of three young girls in a knife attack in Southport, while the rampage unleashed demonstrations in London with echoes of blame on immigrants.
The teen will be remanded in custody and will appear at the Liverpool Magistrates Court on Thursday, the police said.
The 17-year-old was in police custody on suspicion of murder and attempted murder after the bloody rampage on Monday at a "Taylor Swift yoga and dance workshop", a summer vacation event for children aged 6 to 11 in the English seaside town. The three girls killed were aged 6 to 9.
Police said the person charged cannot be named for legal reasons because he is under 18 years of age.
Disturbances in Southport on Tuesday took place after false information was spread on social media that the suspect behind the stabbings was a radical Islamist migrant.
In London on Wednesday, thousands gathered near the prime minister's Downing Street residence, shouting "Save our kids", "We want our country back" and "Stop the boats", as well as English football chants.
Police have said the attack was not terrorism-related and that the suspect was born in Britain, quashing speculation on his origins.
A large number of police wearing helmets formed a barrier around the protesters, who earlier threw flares and smoke canisters towards Downing Street.
The police said in a separate statement that over a 100 people were arrested for offences including violent disorder, assaulting an emergency worker and breaching protest conditions.
Police were braced for further trouble in Southport, where more than 50 officers were injured on Tuesday night in violent clashes. Police vans were set on fire and protesters hurled bricks, bottles and fireworks at officers and cars parked at the town's mosque.
"Just to reassure the communities of Southport, who I am sure are really worried about 'are we going to see this again tonight?' - we are absolutely planning for this evening and for the weekend ahead," Serena Kennedy, chief constable of Merseyside Police, told reporters.