Northern Ireland police appealed for calm Tuesday after a stabbing in Belfast allegedly by a Sudanese suspect and captured in a graphic video prompted calls for anti-immigration protests from UK far-right figures. The Police Service of Northern Ireland (PSNI) vowed to increase its presence on the British province's streets after footage shared online of Monday night's incident drew shock, condemnation and demands for immediate demonstrations on Tuesday evening. Tensions have already been heightened in Britain following violent skirmishes last week in Southampton, southern England, over the police handling of the murder of a young white student stabbed to death by a British Sikh man. Read more'I can't breathe': Protesters attack police at UK rally over student murder The video from Belfast shows a man straddling another man lying in a street and slashing him several times in the head and neck with a knife, in what far-right figures claimed was an attempted beheading. Several people can then be seen intervening, one wielding a hurling stick, and tackling the perpetrator as police arrive. The PSNI said the man arrested on suspicion of attempted murder was in his 30s, Sudanese and in the UK legally, after initially disclosing he was believed to be Somali. Assistant Chief Constable Ryan Henderson said the force had "no information to suggest that this was a terrorist-related incident". The victim, a man in his 40s, "was taken to hospital with significant injuries to his eyes and serious slash wound injuries to his back and face", he told reporters. Officers recovered what is believed to be a kitchen knife at the scene, Henderson confirmed. 'Fear to anger' A 31-year-old mother-of-one who lives nearby said the incident had terrified the neighbourhood. "We're just living in fear now," she said. Prime Minister Keir Starmer called the incident "horrific" and "sickening" on X. The leaders of Northern Ireland's five main political parties issued a joint statement condemning the incident, saying "there is no place in our society for this kind of brutality". "We call for calm and for space to allow justice to take its course," it added. The leaders and police urged people not to share the video, noting its "graphic nature would only serve to retraumatise those involved". But numerous social media accounts linked to so-called "patriots" were sharing the footage, urging people to "protest against mass immigration into their communities". And US tech billionaire Elon Musk retweeted a post by anti-immigration activist Stephen Yaxley-Lennon – also known as Tommy Robinson – adding: "Only by protesting REPEATEDLY and LOUDLY will there be any change!!".