British Prime Minister Keir Starmer was on Monday to hold an emergency meeting in Downing Street after fresh far-right riots broke out across England at the weekend following last week's murder of three children.
Starmer was to chair a Cobra meeting bringing together ministers and police to discuss ways to quell the violence that first broke out in Southport, northwest England, last Tuesday.
Hundreds of people have since been arrested.
Last week the town was the scene of a tragedy in which three young girls were killed and five more children critically injured during a knife attack as they attended a Taylor Swift-themed dance class.
Other riots have broken out in towns and cities across the country, with anti-immigration demonstrators facing off against police, and Muslim counter-protestors in some instances.
On Sunday, Starmer warned far-right protesters that they would "regret" participating in England's worst rioting in 13 years, while Interior Minister Yvette Cooper said there would be "a reckoning".
Far-right behind the riots
Police have blamed the violence on supporters and associated organisations of the English Defence League, an anti-Islam organisation founded 15 years ago whose supporters have been linked to football hooliganism.
Some of the worst violence broke out in Rotherham, northern England on Sunday, where masked demonstrators smashed several windows at a hotel that has been used to house asylum seekers.
According to South Yorkshire Police, at least 10 officers were injured, including one who was knocked unconscious.
There were also large scuffles in the towns of Bolton and Middlesbrough, where rioters smashed windows of houses and cars, leading to 43 arrests.
Late on Sunday, Staffordshire police said another hotel known to have sheltered asylum seekers was targeted near Birmingham.
Shops looted, burnt
The violence is a major challenge for Starmer, elected only a month ago after leading Labour to a landslide win over the Conservatives.
"I guarantee you will regret taking part in this disorder. Whether directly or those whipping up this action online, and then running away themselves," Starmer said in a TV address on Sunday.
There was no justification for what he called "far-right thuggery", promising to bring the perpetrators to justice.
The fresh disturbances came after police said more than 150 people had been arrested since Saturday following skirmishes at far-right rallies.
Rioters threw bricks, bottles and flares at police – injuring several officers – and looted and burnt shops, while demonstrators shouted anti-Islamic slurs as they clashed with counter-protesters.
The violence is the worst England has seen since summer 2011, when widespread rioting followed the police killing of a mixed-race man in north London.
'Wake-up call'
Authorities have said the initial violence was partly caused by false rumours on social media about the background of British-born 17-year-old suspect Axel Rudakubana, who is accused of killing children aged 6, 7 and 9 and injuring another 10 people.
On Monday, Cooper said that social media put a "rocket booster" under the violence.
Agitators have targeted at least two mosques, and Cooper has announced that the government was offering new emergency security to Islamic places of worship.
The rallies have been advertised on far-right social media channels under the banner "enough is enough".
Participants have waved English and British flags while chanting slogans like "stop the boats" – a reference to irregular migrants crossing the Channel to Britain from France.
Anti-fascist demonstrators have held counter-rallies in many cities.
Not all the gatherings have turned violent. A peaceful one in Aldershot, southern England, on Sunday saw participants hold placards that read "stop the invasion" and "we're not far right, we're just right".
At last month's election, the Reform UK party led by Brexit cheerleader Nigel Farage captured 14 percent of the vote – one of the largest vote shares for a far-right British party.