Police last night issue a warning about a possible wave of firebomb attacks in the run-up to Christmas.
Northern Ireland retailers coping with the busy shopping period need to regularly check their premises for incendiary devices, police added.
There have been no specific threats received.
Head of Crime Prevention Inspector David Connery said: “At this busy time of year, we are urging all retailers to be vigilant and on the look-out for anything suspicious.
“Incendiary devices can be left anywhere that can catch fire easily, in garments, soft furnishings and upholstery. They have the potential to destroy property and take human life.
“If something looks out of place, or even just raises concern, contact your local police. Never touch or attempt to move any suspicious looking objects — contact police immediately.”
He is advising managers to review security measures and check premises thoroughly during and after trading.
“An extra few minutes could make the difference, vigilance is the key,” he said.
Crime prevention officers are visiting business and retailers with safety leaflets and posters across Northern Ireland.
Meanwhile, detectives in Londonderry are asking local people to be on the alert against possible cash machine ‘skimming’ incidents.
The warning follows an increase in the number of reports that £200 or £300 have been illicitly removed from bank accounts.
While there have been no allegations of skimming devices found or used recently, police say the thefts may suggest bank details being obtained and cards cloned.
A spokesman said: “Typically, the victims of skimming or card fraud do not realise what has happened until they check their balances or until they try to use a ‘hole in the wall’ machine and find their card refused through lack of funds.
“Any suspicions should be reported to police.”