The United Kingdom has been embroiled in anti-immigration protests after three young girls were killed in Southport last week. British authorities on Thursday said that they were preparing for the possibilities of further unrest in the nation.

Authorities, however, hailed the efforts of anti-racism campaigners and police officers who largely contained a threatened wave of far-right demonstrations overnight.

Prime Minister Keir Starmer cautioned people following the week-long anti-immigrant violence that has severely affected communities from Northern Ireland to the south coast of England. Speaking to reporters at a mosque in Solihull near Birmingham, Starmer said, "It's important that we don't let up here."

The government also declared a national critical incident, deploying 6,000 specially trained police on standby to respond to any unrest or clashes.

Police said that largely the protests and counter-protests were peaceful, with a small number of arrests.

“The show of force from the police and, frankly, the show of unity from communities together defeated the challenges that we faced,” said Commissioner Mark Rowley, the head of London's Metropolitan Police Service, adding that, "It went off very peacefully last night, and the fears of extreme right disorder were abated.”

However, tensions continued to remain high after right-wing protestors fueled violence by spreading misinformation about the suspect's identity in a knife attack that left three young girls dead in Southport. Police said that the last child hospitalised in the July 29 stabbing has been discharged.

Police have made nearly 500 arrests after anti-immigrant mobs clashed with the forces, attacked mosques and overran two hotels giving shelter to asylum-seekers.

One of the man arrested, in his 50s, was nabbed on suspicion of "encouraging murder". This came after a local Labour councilor allegedly called for far-right protestors' throats to be "cut", The Associated Press reported.

Meanwhile, the Labour Party suspended Ricky Jones, who is alleged to have made the 'cut' remark during a London demonstration on Wednesday.

The Starmer-led government has vowed to track down and prosecute those responsible for the unrest, including those who incite violence online.

Starmer -- at an emergency meeting with law enforcement officers at his office -- said that police need to remain on "high alert".

He acknowledged the strategic police staffing and swift justice for rioters in courts as factors in minimising the trouble the night before.

Police across the UK prepared braced themselves for further far-right clashes after activists circulated a list of over 100 sites they planned to target, including offices of immigration lawyers and those offering services to migrants.

However, the demonstrations failed to materialise as police and counter-protestors filled up the streets, carrying signs of "Refugees Welcome" and chanting "Whose streets? Our streets."

To ensure that people are prevented from taking part in the unrest in the future, TV cameras were allowed into the Liverpool Crown Court on Thursday as Judge Andrew Menary sentenced two men to 32 months in prison.

Prosecutors at the hearing played videos of rioters pelting bricks at the police and setting ablaze garbage cans.

“It seems to me there were hundreds of people observing, as if this was some sort of Tuesday night entertainment,” Menary said, adding that “All of them should be frankly ashamed of themselves.”

Meanwhile, Northern Ireland's regional legislative assembly convened on Thursday to respond to the widespread disorder.

Minister for Justice Naomi Long said the violence and racist attacks in recent days were "not reflective" of the people of Northern Ireland.

"We need to call it for what it is. It is racism, it is Islamophobia, it is xenophobia. If we're going to deal with it, we need to name it for what it is, and we need to challenge it," Long said.

Reportedly, the government is also considering imposing sanctions other than jail time including banning rioters from soccer matches. There should be consequences for those implicated in unrest, Home Office minister Diana Johnson told LBC radio.

"I think all options are being looked at, to be honest, and I am pretty clear that most football clubs do not want to be seen to have football hooligans and people carrying out criminal acts on the streets of the local communities in their stands on a Saturday," Johnson said.