The PSNI is deploying officers in plain clothes to tackle crime in Derry city centre.
The PSNI shared a photograph on social media of three officers who were undercover in the city centre on Tuesday. The officers' faces cannot be seen in the photograph.
"Did you notice these dodgy looking characters around the city centre today? If you did it was police from local policing team four in plain clothes," wrote the PSNI on social media.
"We were working in partnership with local businesses to disrupt shop lifting, drug activity and anti-social behaviour. Why were we there? Because retail crime, drug use and anti-social behaviour are issues that matter to you. As a result of the patrol, one adult male was reported to the PPS for an indecency offence."
The PSNI encouraged anyone with information in relation to city centre crime to contact them.
"If you see suspicious activity or know of anyone involved in drugs, please let us know. Call 999 in emergencies and 101 for non-emergencies. Alternatively you can call crime stoppers and report this anonymously on 0800 555 111."
Some people praised the initiative whilst others questioned why the PSNI would reveal details of undercover operations to the public.
"Why advertise the fact that constables are wandering around the town in plain clothes?," asked one man.
"Undercover policing - Smart. Advertising it on social media - NOT SMART," he added.