Dozens of arrests have been made as disorder following the Southport knife attack spread to different parts of the country.
More than 100 people were arrested in central London on Wednesday evening as officers clashed with protesters on Whitehall during a demonstration.
Unrest also broke out in Hartlepool where eight people were arrested, several officers were injured and a police car was set on fire.
Prime Minister Sir Keir Starmer planned to meet on Thursday with senior police leaders to offer them his "full backing".
Also on Thursday, a 17-year-old boy appeared in court, charged with murdering three girls and attempting to murder eight other children and two adults in Monday's knife attack.
Dal Babu, former Chief Superintendent and firearms commander in the Met, has blamed the disorder on the "reckless" spread of misinformation about the identity of the suspect charged in the stabbing.
Speaking on OceanNewsUK, Mr Babu said the police have taken the "unprecedented" decision to confirm the suspect "was born in this country".
In London, demonstrators were seen launching flares towards the gates of Downing Street and at a statue of Winston Churchill.
People could be heard chanting phrases such as "stop the boats" and "save our kids" as they threw bottles and cans at officers.
Earlier, the Met said conditions placed on the protest had been breached.
The Met said it made arrests for a range of offences including violent disorder, assault on an emergency worker and breach of protest conditions on Wednesday evening.
In a statement, the Met said officers were deployed to "ensure disorder was contained" and that some "suffered minor injuries".
Several officers were also injured in Hartlepool after violence broke out in the town, Cleveland Police said.
Eight people were arrested in relation to public order offences after glass bottles and eggs were thrown at police by protesters. A police car was also set on fire.
Ch Supt David Sutherland said of the Cleveland arrests: "At this stage we believe the protest is in connection with the incident in Southport earlier this week."
The force said they "expect further arrests to be made in the coming days".
Disorder was also reported in Aldershot. Local MP Alex Baker said a peaceful protest "descended into intimidating behaviour" at a hotel in the Hampshire town.
"This incident was exacerbated by people from outside our community who came here determined to cause unrest," she said.
"We all support our shared right to peacefully protest, but we will not stand for people coming to our towns determined to stir up trouble and divide out community."
In Manchester, two men were arrested for violent disorder and assaulting an emergency worker.
Greater Manchester Police said protesters were dispersed in the Newton Heath area after "objects were thrown, towards the police and public".
Wednesday's disorder followed unrest near a mosque in Southport on Tuesday night, during which the building was attacked.
Merseyside Police officers were also pelted with bricks and a police van was set on fire.
The unrest came after Alice Dasilva Aguiar, nine, Bebe King, six, and Elsie Dot Stancombe, seven, were fatally stabbed on Monday while attending a Taylor Swift-themed dance class in Southport.
Eight other children suffered knife wounds - with five of them in a critical condition - while two adults were also critically hurt.
On Thursday, Alder Hey Children's NHS Foundation Trust announced two of the injured children had been discharged.
Five children are still being treated by the hospital and are "currently in a stable condition", Alder Hey said.
Accused appears in court
The 17-year-old, Axel Muganwa Rudakubana, has been charged with three counts of murder, 10 counts of attempted murder and possession of a bladed article.
He appeared at Liverpool City Magistrates' Court on Thursday morning and later at Liverpool Crown Court. He was remanded into youth detention accommodation until 25 October, when a pre-trial preparation hearing will take place.
The teenager was previously not named because of his age, but Recorder of Liverpool Judge Andrew Menary KC ruled during the hearing that his identity could be made public.
The judge said this was "principally" because the defendant turns 18 on 7 August and legal restrictions protecting his anonymity would have ended then. He added: "Continuing to prevent full reporting at this stage has a disadvantage of allowing others up to mischief to continue to spread misinformation in a vacuum."
Merseyside Police have confirmed that the defendant was born in Cardiff to Rwandan parents, that he appears to have no known links to Islam, and that they are not currently investigating the attack as terror-related.
The prime minister will welcome senior policing leaders to Downing Street to discuss the resulting unrest.
Number 10 said the meeting would "offer them the government’s full backing following multiple high-profile incidents of extreme violence and public disorder on our streets".
"[The prime minister] will say that the shocking events in Southport this week serve as a reminder of the bravery of our emergency service workers and the vitally important work they do to keep the public safe," it said.
"While the right to peaceful protest must be protected at all costs, he will be clear that criminals who exploit that right in order to sow hatred and carry out violent acts will face the full force of the law."
