Paramedics were treating four people and police said early enquiries suggested several people had been stabbed in an incident at the Arndale shopping centre in the northern English city of Manchester on Friday.
“Officers are in attendance and early enquiries suggest that several people have been stabbed,” Greater Manchester Police said in a statement.
“A man in his 40s has been arrested on suspicion of serious assault. He has been taken to custody for questioning.”
They gave no further details about the incident.
Media reports said the city-centre shopping centre had been evacuated, with large numbers of police and paramedics in attendance.
Pictures taken at the scene and posted on social media showed officers using a stun gun on a man.
“We are on the scene, we are treating four patients,” a spokeswoman for the North West Ambulance Service said.
David Allinson, Centre Director for Manchester Arndale, told the Manchester Evening News that there had been a serious incident.
“The centre has been evacuated while police investigate the incident,” he said.