Hundreds of protesters, many with their faces covered, attacked police and burned vehicles in a number of locations across Northern Ireland on Tuesday night after a video of the attack, in which the victim lost an eye, went viral.
Political leaders said the violence was aimed at ethnic minorities.
"It is clear that people were targeted last night because of their background and I will not tolerate it," British Prime Minister Keir Starmer said in a statement, adding: "Those responsible will feel the full force of the law."
The suspect in the attack in north Belfast, a 30-year-old Sudanese national named as Hadi Alodid, appeared in court on Wednesday where he was remanded in custody.
The victim, in his 40s, suffered significant injuries to his face and back, the court heard.
Videos of the attack circulated online all day on Tuesday, sparking calls for violent protest on social media.
Police had to help one family escape from a burning house. Several cars and a bus were set on fire and reduced to shells.
Local politicians and a pastor said many of those who were targeted were Black.
"There can be no excuse and no justification for these attacks," Northern Ireland's First Minister Michelle O'Neill said.
"Groups of masked men burning families out of their homes is nothing less than disgusting cowardice."
The attack, which is not being treated as terrorism, comes at a time of heightened tensions in Britain following the murder of a student who was handcuffed by police as he lay dying from stab wounds after his killer, a Sikh man, falsely alleged a racist attack.
It also follows repeated protests about immigration, with populist parties saying Britain's asylum policy had allowed dangerous men into the country.
Northern Ireland's Justice Minister Naomi Long told Reuters that "bad-faith actors" who would have previously struggled to find the province on a map had sought to weaponise the understandable fear and anger sparked by the knife attack to target those who had the same skin colour.
"We know in Northern Ireland the damage that can do when you demonise a whole group of people because of the behaviour of a few, and we do not want to go back there," she said.
Smaller protests were reported elsewhere across Britain on Tuesday evening, including in London, where demonstrators briefly blocked Parliament Square, and in Scotland's two largest cities, Glasgow and Edinburgh.
The disorder in Northern Ireland is the latest violence to flare in the UK in response to a crime, often believed to involve a migrant, which has led to calls from some prominent anti-Islam and anti-immigrant activists for people to "take to the streets".
Belfast pastor Jack McKee told the BBC that some members of his church, who had lived there for 20 years, were "getting put out just because they're Black".
Immigration has historically been low in Northern Ireland due to the three-decade conflict waged between mainly Catholic Irish nationalists seeking Irish unity and predominantly Protestant pro-British "loyalists" wanting to stay in the United Kingdom, and the British military.
Migration has been increasing in recent years however, and there has been a hardening sentiment against it in both Northern Ireland and parts of the Republic of Ireland.
Northern Ireland was also hit by anti-immigrant rioting in 2025 amid anger over an alleged sexual assault.
Charges against two boys were later withdrawn by prosecutors.
