The King has visited Southport in northern England to pay tribute to the victims and families of those who witnessed a mass stabbing that sparked nights of riots and racist attacks targeting Muslims and migrants.

Three young girls were killed and others were wounded in the July 29 attack, which sparked the riots after online misinformation wrongly said it had been committed by an Islamist migrant.

A 17-year-old male, who police have said was born in Britain, has been charged with three counts of murder, 10 counts of attempted murder and one of possessing a bladed article.

The King has praised the community spirit, compassion and resilience that countered aggression and criminality from the rioters, and said he hoped mutual respect and understanding would continue to unite the nation.

On Tuesday (UK time), the monarch met some of the surviving children who were there when the Taylor Swift-themed dance class was attacked, and their families.

He also met and thanked representatives from local emergency services and community groups.

The King set up the Princes Trust charity in the 1970s. It has helped a million young people to find work or create community projects and has worked in areas affected by riots and unrest over the years.

It has continued to operate since he became sovereign.

-AAP