Masked raiders burst into a flat in Preston and attacked the occupants before stealing mobile phones.
Police said two women and three men were attacked in the raid, which happened in Livesey Street in the Frenchwood area of the city.
Just after midnight on Saturday the group, aged between 16 and 22, were in the flat when three masked men burst in and began threatening them with violence.
One of the attackers was armed with a metal bar.
Two of the men were assaulted while the intruders searched the property, before stealing mobile phones and other items.
One of the men suffered a deep cut to his face and bruising in the assault.
All three attackers are described as Asian, wearing dark clothing with part face coverings. All three were in their late 20s.
The tallest was described as having a big quiff hairstyle and one was of chubby build.
Det Sgt Jerry Sturgess, of Preston CID, said: “It isn’t clear at this time what the motive was for this attack and whether the intruders have mistakenly attacked this address.
“I urge anyone with any information at all to come forward.”
Anyone with information about the incident or about the offenders can contact police on 101 quoting log reference 0046 of May 7.
Alternatively, contact Crimestoppers anonymously on 0800 555 111 or online at Crimestoppers-uk.org.