Police are investigating an aggravated burglary which occurred at a flat in the Ard Grange area of Derry in the early hours of Sunday.
As a result of the incident a 21 year-old man was treated in hospital for head injuries, which are not life threatening.
Another 21 year-old man was arrested and has subsequently been released on police bail pending further enquiries.
Detective Constable Donnell, from Reactive and Organised Crime at Strand Road, said: “Police are keen to speak to anyone who may have witnessed a number of males in the street sometime around 3.30-4 am. If you were in the area and have any information that would be of assistance to the investigation, please contact police on 101.
“Alternatively, information can be given anonymously through the independent charity Crimestoppers on 0800 555 111.”