Police forces have made at least 100 arrests across the UK.
The murders were seized on by anti-immigrant and anti-Muslim groups as misinformation spread that the suspected attacker was an immigrant and a radical Islamist. Police have said the suspect was born in Britain. Media reports have said his family is Christian.
Violent disorder broke out in cities around the country on Saturday, including Liverpool, Bristol and Manchester, resulting in dozens of arrests as shops and businesses were vandalised and looted and several police were injured, police statements said.
The government has promised tough action against people taking part in the violence. On Sunday, hundreds of anti-immigration protesters gathered by a hotel that has been used to house asylum seekers near Rotherham, northern England.
The protesters threw bricks at police and broke several hotel windows, a Reuters witness said, before setting bins on fire. Dozens of other protesters gathered by another such hotel in Aldershot, southern England. Downing Street has confirmed there will be an emergency response meeting on Monday after more than 150 people were arrested following violent disorder in UK towns and cities over the weekend.
It comes after Sir Keir Starmer condemned an attack on a hotel housing asylum seekers in Rotherham and promised those involved in unrest would face "the full force of the law".
Police responded to violent scenes in Rotherham, Middlesbrough, Bolton and other parts of the UK on Sunday.
The Cobra meeting will come after a sixth day of escalating violence following the fatal stabbing of three young girls in Southport last week.
Reuters Rioters toss a trash bin during an anti-immigration protest in RotherhamReuters
Rioters toss a trash bin during an anti-immigration protest in Rotherham
Cobra meetings, or Cobr meetings as they are often also called, are named after Cabinet Office Briefing Room A on Whitehall.
It is an emergency response committee, a get together of ministers, civil servants, the police, intelligence officers and others appropriate to whatever they are looking into.
Monday's meeting of the emergency committee will be intended to provide the government with an update on the violence over the weekend and the response in the coming days. It will involve relevant ministers and police representatives.
Sources have suggested this should be seen in the context of meetings that have already taken place, such as one between the prime minister and police chiefs last Thursday, and a meeting of senior ministers on Saturday.
PA large crowd of men scream and shout at a line of police officers in riot gear and sheilds.PA
Police say 700 people gathered outside a Holiday Inn Express
During the prime minister's televised address on Sunday, he warned those involved that they will "regret" taking part.
"People in this country have a right to be safe, and yet we've seen Muslim communities targeted, attacks on mosques," the prime minister said.
"Other minority communities singled out, Nazi salutes in the street, attacks on the police, wanton violence alongside racist rhetoric, so no, I won't shy away from calling it what it is: far-right thuggery."
Police officer injured after second hotel targeted in Tamworth
Faith leaders urge communities to 'remember what unites us
In a statement, the Home Office offered mosques greater protections as part of a new process, under which it said "rapid security" deployment can be requested in order to allow a return to worship as fast as possible.
In Rotherham, at least ten police officers were injured with one left unconscious after anti-immigration demonstrators threw planks of wood at officers and sprayed them with fire extinguishers, South Yorkshire police said.
Some members of the group smashed windows to gain access to a Holiday Inn Express and a large bin was set alight.
The officer knocked unconscious suffered a head injury, the force said, adding that at least two others had suspected broken bones.
Hotel employees and residents, some of whom are asylum seekers, were "terrified", but no injuries were reported, police said.
Home Secretary Yvette Cooper called the scenes "utterly appalling" and said police have government backing to take "the strongest action".
At a second hotel in Tamworth, Staffordshire, officers said they had to deal with "violent acts of thuggery" on Sunday evening.
One officer was injured at the site as people threw missiles, smashed windows, and started fires, Staffordshire Police said.
Meanwhile, a group of rioters in Middlesbrough smashed the windows of houses and cars and hurled objects at officers.
In Dorset, 600 people from opposing sides gathered on the seafront in Weymouth. Officers said there had been a "small number of low-level incidents", with one man arrested for a public order offence.
And in Bolton, anti-immigration protestors were confronted by a group of up to 300 masked people shouting "Allahu Akbar" - or "God is greatest".
Greater Manchester Police issued a Section 60AA order in the town which requires people to "remove face coverings used to disguise or conceal their appearance".
The violence followed similar scenes of unrest in Southport, Belfast, Hartlepool, Hull, Liverpool, Stoke-on-Trent, Nottingham, Sunderland and elsewhere earlier in the week.
Sir Keir indicated the response to the violence could mirror elements of how the 2011 riots were handled, at which time he was director of public prosecutions.
"We do have standing arrangements for law enforcement which means that we can get arrests... and convictions done very quickly," he said.
"I myself was part of that in 2011 when I was director of public prosecutions, and I'm determined we will do whatever it takes to bring these thugs to justice as quickly as possible."
Ministers have suggested that courts could sit 24 hours to fast-track prosecutions - as they did in 2011 - while police forces have measures in place to draft in extra officers to tackle potential unrest.
