Police were called around 18:18hrs on Wednesday, 10 January to a branch of Tesco Express in Belsize Road, Hampstead, following reports of a knifepoint robbery.
Two males wearing crash helmets are believed to have entered the premises and threatened staff before demanding cash. They then fled on a moped with a sum of money.
Officers attended along with specialist Trojan officers following reports that one of the males was armed with a firearm.
There have been no reported injuries.
There have been no arrests.
A crime scene is in place.
A further scene is in place in Byron Court after officers discovered items believed to be linked to this incident.
Officers from the Central North Command Unit investigate and would ask anyone who was in the area and saw anything suspicious, or was a witness to this incident, to please contact police on 101, or CID at Islington Police station directly on 0208 345 0316.