Four people have been injured in a knife attack at the Arndale shopping centre in Manchester city centre.
A man in his 40s has been arrested by police on suspicion of terrorism offences.
Prime Minister Boris Johnson tweeted: "Shocked by the incident in Manchester and my thoughts are with the injured and all those affected."
The shopping centre has been evacuated and trams stopped operating outside the entrance to the shopping centre.
Counter Terrorism Police North West are now investigating the motivation behind the attack.