The police are asking the public to be extra vigilant in the run-up to Christmas after the discovery of incendiary devices in recent months.
Businesses are being asked to review security measures and to check their premises while shoppers have been urged to report anything suspicious.
Assistant Chief Constable Duncan McCausland said extra police officers have already been put on the streets.
"We have already dealt with a number of real and hoax devices," he said.
"We would urge everyone to look out for anything suspicious. If you see something that looks out of place, or even just raises concern, report it immediately to the police.
"We hope that increased police activity will work to disrupt criminals and help ensure that Northern Ireland is a safer place to live, work and, importantly at this time of year, to shop."