Politicians from across the spectrum have called for calm after a stabbing in Belfast, Northern Ireland.There are fears that there could be widespread disorder after figures on social media including Elon Musk called for people to fill the streets in protest against immigration. The alleged perpetrator of the attack, which was filmed and shared widely online, was revealed today as an asylum seeker from Sudan.The attack happened at about 10.30pm on Monday outside a block of flats in north Belfast. Graphic video shared on social media showed a man straddling another man on the ground and striking at his head and neck.The clip showed people intervening to stop the assault, with one man, later named locally as Maitiu Mag Tighearnan, using a hurling stick against the attacker multiple times.Police said the arrested man was believed to be Sudanese and in his 30s. They had initially said he was thought to be from Somalia. The victim, who has not been named, is in his 40s.As of Tuesday evening, the suspect was in custody and the victim was in a serious condition in hospital. Police said the victim had serious injuries to his eyes, and serious slash wounds to his back and face.Figures from across the world have taken to social media to call for protests against immigration. Some posts from accounts in Northern Ireland announce that roads are “closed” for a protest and warn that all businesses in the area should shut at 5.30pm to prepare for disorder.Stephen Yaxley-Lennon, a far-right agitator who refers to himself as Tommy Robinson shared the video of the attack on Monday night and posted a call for protests in central London and elsewhere in the UK.Sudanese business owners on Sandy Row, a loyalist area of central Belfast, closed their stores with steel shutters by 4pm and said they planned to stay at home that night.