The PSNI say officers received a report around 2.50 am that two men and a woman, all aged 19, were sitting in a parked red Volkswagen Golf when a white Seat Ibiza pulled up at Strand Road in Derry.
Two males, one of which was armed with a knife and a suspected firearm, got out of the Ibiza.
They made the three people get out of the Golf and both got into the car. Both the Leon and the Golf then made off in the direction of Culmore Road.
The three people from the Golf were not injured in the incident.
Anyone with any information about this is asked to contact CID in Strand Road Police Station on the new non-emergency number 101. Or if someone would prefer to provide information without giving their details, they can contact the independent charity Crimestoppers and speak to them anonymously on 0800 555 111.