A man in his 40s was arrested on suspicion of serious assault. (Representational)

Counter-terror police were on Friday probing a mass stabbing at a shopping centre in northwest England that left five people injured and needing hospital treatment.

The attack happened at the Arndale shopping centre in the heart of Manchester, where an Islamist extremist suicide bomber killed 22 after an Ariana Grande concert in 2017.

"We can confirm that five people have been stabbed and taken to hospital," Greater Manchester Police said in a statement.

"Given the location of the incident and its nature officers from Counter Terrorism Police North West are leading the investigation as we determine the circumstances," it added.

Officers were "keeping an open mind about the motivation", the force said.

A man in his 40s was arrested on suspicion of serious assault.

Footage posted online appeared to show one police officer restraining a suspect on the floor as another stands over him pointing a Taser.

Another photograph circulating on social media showed paramedics screening off a cafe to treat victims after the shopping centre was evacuated.

Shop worker Jordan, 23, told Britain's domestic Press Association news agency that "a man was running around with a knife lunging at multiple people, one of which came into my store visibly shaken with a small graze."

North West Ambulance Service said it had treated five people after being called at 11:17 am (1017 GMT).