Two masked men armed with hammers stormed a Spar store and threatened two staff members.
The men stole money and cigarettes before leaving the store, with police believing they may have left the area in a blue vehicle.
The heist took place at around 9 p.m. on Wednesday at the Spar store on Wood Lane in Heskin near Chorley.
Both attackers are white, in their early twenties, of medium build, wearing hoods and dark clothing.
They spoke with Nordic accents.
DC Philip Hampson of Chorley CID said: “This is a shocking incident that must have been terrifying for the victims who have been threatened by these men in their workplace.
“Fortunately, they were not physically injured during the flight, but were naturally extremely shocked and shaken up.
“These individuals were prepared to use weapons to steal and we are following a number of investigative leads to identify them.
“I appeal to anyone who thinks they know who the people in the CCTV footage are or who may have been in the area at the time and saw something suspicious, especially a blue vehicle, to Contact us.
“I would especially like to appeal to anyone with a dash cam or CCTV footage to get in touch.”
Anyone with information should contact the police on 101 citing log number 1373 for December 1 or can email [email protected]
You can send CCTV or dash camera images to the police here: unitedkingdom1cpp-portal.digital-policing.co.uk/lancashire/appeal/staff-threatened-in-heskin-shop-robbery
Alternatively, an independent Crimestoppers charity can be contacted confidentially on 0800 555111 or online at crimesstoppers-uk.org.