A man has been arrested on suspicion of assault and possession of an offensive weapon after an incident in a Lancaster square.
Police were called at 4.38pm on Thursday to a report of a disturbance in Dalton Square involving a group of men and women.
A Lancaster Police spokesperson said: "Our officers attended and it was found that a man in his 20s had been assaulted.
"He was taken to hospital for treatment.
"We appreciate that children and families were in the area for Light Up Lancaster, and we will not tolerate such behaviour.
"Extra patrols will be in the area to provide reassurance today."
A 24-year-old was arrested on suspicion of assault causing actual bodily harm and possession of an offensive weapon, and is currently in custody.