A 28-year-old man has been left critically ill in hospital after being attacked in Derry.
The incident happened in the Cornshell Fields area of the city in the early hours of Monday.
Police said they received a report shortly after 2am that the victim had been attacked in a house in the area.
"He was taken to hospital for treatment for potentially life-threatening injuries where his condition is described as critical," a PSNI spokesman said.
"Three other men and two women, who were also in the house at the time, were not injured.
"Four males, who are believed to have been involved in the incident, are reported to have made off in a grey-coloured Volkswagen Golf."