In an unusual move, a British court on Thursday named the 17-year-old suspect in a stabbing rampage that left three children dead and eight injured in northwestern England early this week. The suspect, Axel Muganwa Rudakubana, appeared in a court in Liverpool to face three counts of murder, 10 counts of attempted murder, and possession of a bladed article.

The stabbing spree, at a Taylor Swift-themed dance class in the town of Southport on Monday morning, stunned the country and ignited two days of racially fueled riots that were incited by far-right provocateurs.

Two girls — Bebe King, 6, and Elsie Dot Stancombe, 7 — died of their injuries on Monday, the police said, while a third, 9-year-old Alice Dasilva Aguiar, died in the hospital early Tuesday. Of the eight injured children, five remain in the hospital, all in stable condition, the authorities said on Thursday.

As the traumatized town mourned the children, rioters flooded into the streets. More than 50 police officers were injured as demonstrators threw bricks at a mosque, attacked the police, set cars on fire and damaged a convenience store.

A day later, the unrest spread to the streets near 10 Downing Street, where protesters clashed with police officers, resulting in more than 100 arrests. London’s mayor, Sadiq Khan, condemned the violence as “completely unacceptable.”

The outbreak of unrest poses an early test to Prime Minister Keir Starmer, less than a month after his Labour Party won a landslide election victory. Mr. Starmer, a former director of the public prosecution service, oversaw multiple cases that involved the balance between freedom of expression and public order.

In a visit to Southport on Tuesday, Mr. Starmer paid respects to the victims and their families. They were “going through raw pain and grief that most of us can’t imagine, I can’t imagine as a dad myself,” he said.

This is a developing story.