Paramedics had called the police shortly after 3pm after finding a man with serious injuries at a parade of shops near Lambton Grove.
Shortly before 3.30pm, police heard that another man had turned up at a hospital with a stab wound to his arm.
The man with the stab wound has been arrested in connection with the incident, police said.
Update from First Bus
SERVICE UPDATE** - Roundhay road is likely to be closed for for the following 2-3 hours. We are anticipating Major delays around Leeds and Roundhay road as a result and apologise for any disruptions for any journeys affected. ^Khizar
The full police statement
At 3.17pm today (19/11) police were contacted by the ambulance service who were attending Roundhay Road, Harehills.
A man was found with serious injuries at a parade of shops near to Lambton Grove and is undergoing treatment.
A 3.28pm police received a report of a man attending hospital with a stab wound to his arm. He has been arrested in connection with the incident.
ï»¿A scene is currently cordoned off in Roundhay Road and a road closure is in place while enquiries into the incident continue."