It marks the monarch's first intervention since the unrest began last week.
The king thanked police and emergency services for their response to the disturbances and he welcomed the way that community groups had countered "the aggression and criminality from a few," a Buckingham Palace spokesman said in a statement.
"It remains His Majesty's hope that shared values of mutual respect and understanding will continue to strengthen and unite the nation."
The King has talked by telephone with Prime Minister Keir Starmer and police chiefs.
Nearly 600 people have been arrested and more than 175 have appeared in court during the riots. (EPA PHOTO)
Thousands of specialised police officers are due to remain on duty this weekend in case the rioting resumes after three days of calm.
During a visit to the Metropolitan Police's special operations room in Lambeth on Friday, Starmer said strong policing and swift justice have had an impact.
"But we have to stay on high alert going into this weekend because we absolutely have to make sure that our communities are safe and secure and feel safe and secure," he said.
The riots broke out across the country after online posts falsely identified the suspected killer of three young girls in a knife attack on July 29 in Southport, northwest England, as an Islamist migrant.
Meanwhile, a man who used social media to stoke racial hatred and encouraged people to torch hotels housing asylum seekers was sentenced on Friday to more than three years in prison.
The term handed down to Tyler Kay, a 26-year-old father of three, was among the harshest sentences so far for people who have taken part in or encouraged the latest rioting in Britain.
"You posted as you did because you thought there were no consequences for yourself from stirring up racial hatred in others," Judge Adrienne Lucking told Kay in Northampton Crown Court.
"I am sure that when you intentionally created the posts, you intended that racial hatred would be stirred up by your utterly repulsive, racist and shocking posts that have no place in a civilized society," Lucking said.
Earlier in the day, Jordan Parlour, 28, was sentenced 20 months in prison for encouraging Facebook followers to attack a hotel in Leeds that housed migrants because he was frustrated with immigration problems in the United Kingdom.
So far, nearly 600 people have been arrested and more than 175 have appeared in court, the Ministry of Justice said.
The government has pledged to track down and prosecute those responsible for the disorder, including people who incite violence online.
with AP
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