A man is being treated in hospital after suffering knife wounds when he was attacked by four men in Lincoln.
The 25-year-old North Hykeham man sustained cuts to his hands, face and abdomen during the assault in a passageway off St Botolphs Court.
His condition is not life-threatening but police said "the nasty incident could have turned out far worse".
A knife has been recovered but it is not yet known if it is the weapon used in the attack on Wednesday evening.
Detectives are also trying to establish whether a white Transit type van seen in the area is connected to the offence.
Anyone with information about the attack, which took place at about 2000 BST, should contact the Lincolnshire force.