Counter terrorism police are leading an investigation after a knifeman attacked multiple people at a shopping centre in Manchester.
A man in his 40s has been arrested on suspicion of the commission, preparation and instigation of an act of terrorism.
Greater Manchester Police confirmed that three people have been stabbed and one more injured in the incident at the Arndale shopping centre just before midday.
A 19-year-old woman and another woman are in a stable condition, having been taken to hospital with stab wounds.
A man in his 50s has also been taken to hospital with stab wounds and a fourth victim - a woman in her 40s - who was not stabbed - has been assessed and did not need to go to hospital following assessment by paramedics.
Assistant Chief Constable Russ Jackson said: "We do not know the motivation for this terrible attack. It appears random, is certainly brutal and of course extremely frightening for anyone who witnessed it.
"We have arrested the man, a male in his 40s, on suspicion of terrorism because of the nature and circumstances of this attack."
Boris Johnson reacted to the incident on Twitter saying: "Shocked by the incident in Manchester and my thoughts are with the injured and all those affected.
"Thank you to our excellent emergency services who responded and who are now investigating what happened."
Shop worker Jordan, 23, said the knifeman had been “lunging at multiple people”.
“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.
“Soon after, security staff told all retail staff to close their doors and move the public to the back of the stores,” he added.
A large section of road has been cordoned off outside Arndale, where a police helicopter hovers overhead.
Shoppers claimed on Twitter that they had been evacuated from the centre and other social media posts showed a large number of officers at the scene and a suspect being Tasered by police.
Anyone with information can contact the police on 101 or anonymously via Crimestoppers on 0800 555 111.