A number of people have been taken to hospital, Sky News reports. It is not known how many have been injured or how serious their injuries are. At least two ambulance helicopters have flown injured people to hospital, according to the local ambulance service, which describes the operation as "large-scale".
Two men were arrested at Huntingdon train station after more than 30 officers were called to the scene. A major police operation was still underway at 11.30pm, Swedish time, but the circumstances surrounding the incident remain unclear.
Prime Minister Keir Starmer wrote on social media that the “horrific incident” was deeply concerning. He also urged the public to follow police advice and stay away from the area.
