Police arrested a suspect in connection with a stabbing in Belfast, Northern Ireland, after graphic videos of the attack spread online. The victim sustained serious injuries, and political leaders are calling for calm.

UK Prime Minister Keir Starmer’s office called for calm on Tuesday after police said they arrested a Sudanese suspect over a stabbing in residential Belfast in Northern Ireland that drew national attention because of graphic videos of the attack online. Police said the victim was taken to the hospital with serious wounds to his face, neck and back late on Monday. They said the suspect, who is in his 30s, was arrested on suspicion of attempted murder and remained in police custody. A kitchen...