A "standing army" of specialist police will be set up to deal with rioting and the justice system will be ramped up to handle hundreds of arrests after violent disorder rocked cities across the United Kingdom, Prime Minister Keir Starmer said Monday. 

Starmer convened an urgent meeting after lawlessness blamed on far-right activists and misinformation on social media whipped up anger over a stabbing rampage at a dance class last month that left three girls dead and many more wounded. 

"Whatever the apparent motivation, this is not protest. It is pure violence and we will not tolerate attacks on mosques or our Muslim communities," Starmer said. "The full force of the law will be visited on all those who are identified as having taken part in these activities."

False rumors spread online that the suspect was a Muslim and an asylum seeker, which led to the attacks on immigrants and Muslims. Police have said the suspect was born in Britain and are not treating it as a terrorist incident. A 17-year-old boy was charged and named in a U.K. court last Thursday, partly to counter misinformation about his identity that has been blamed for triggering the riots.

WATCH | Violent anti-immigration protests in U.K. partly fuelled by misinformation 

Violent anti-immigration protests in U.K. partly fuelled by misinformation

Violent far-right anti-immigration protests spread across the U.K over the weekend, fuelled in part by online misinformation about the suspect in a deadly stabbing attack at a children's dance party.

On Sunday, angry mobs attacked two hotels used to house asylum seekers, breaking windows and lighting fires before police dispersed the crowds and residents were evacuated. Dozens of police officers have been hospitalized for injuries in the past six days after being struck with bricks, bottles and large wooden posts.

Oliver Coppard, the mayor of South Yorkshire, where one of the hotels was attacked, attributed the violence to "far-right thugs."

"As Keir said, as every decent person has said, I think these are far-right thugs who attacked some of the most vulnerable people in our communities and there is absolutely no excuse," Coppard told the BBC. "There can never be any excuse for trying to burn to death 200 of the most vulnerable people in our community."

Starmer's spokesperson said after the meeting that social media companies have not done enough to prevent the spread of misinformation that has fuelled far-right violence. They vowed that anyone who stokes the disorder — online or on the streets — could face prison.

The National Police Chiefs' Council said 147 people had been arrested since Saturday evening and more would follow in the coming days.

Some of that false and misleading information has come from foreign states, according to the spokesperson.

"The disinformation that we've seen online attracts amplification from known bot activity, which, as I say, can be linked to state-backed activity," the spokesperson said in a read-out of the meeting.

A spokesperson for Starmer said no requests have been made to call in the army.

The Home Office, which is responsible for law and order, has offered mosques greater protection under a new "rapid response process" designed to quickly tackle the threat of further attacks on places of worship.