Counterterror police are now leading an investigation into a stabbing incident that injured five people at a shopping center in northwestern England, as police keep an open mind on the motive.

Greater Manchester Police said a man in his 40s has been arrested on suspicion of serious assault.

'In these early stages, we are keeping an open mind about the motivation of this terrible incident and the circumstances as we know them,' 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,' police said.

The North West Ambulance Service informed that it treated four people in the stabbing after being called to the Arndale shopping center on Friday.