A taxi driver has been arrested after footage on social media appeared to show a passenger being threatened with a suspected gun.
The driver has also had his contract with Fonacab terminated after the video emerged online.
The footage showed the man pointing the suspected firearm at a man in the passenger seat of his vehicle, and striking him in the face with the weapon.
Police said a 48-year-old man has been arrested “on suspicion of a number of offences including possession of a firearm or imitation firearm”.
The man remains in custody as police continue with their enquiries.
The disturbing footage, which has been circulated on social media, shows the driver warning the man to "work your f*****g debt off", while telling him he was "lucky I'm not taking your f*****g knees out".
Fonacab said in a statement on Thursday that the driver had logged off and was not working when the dashcam footage of the interior of the vehicle was recorded.
The footage also shows another male in the rear seat of the vehicle who tells the driver he was "shaking like a leaf" over the confrontation.
In the video, the driver is heard stating to the man: "See what happens in this car, see if I hear anyone talking about it, I will take your f*****g head off."
Fonacab said it became aware of the footage on Wednesday evening, and the driver was interviewed by the firm the following morning, following which "his relationship with fonaCAB (was) immediately terminated".
The company said it is liaising with the PSNI and the Driver & Vehicle Agency (DVA), adding: "Due to the nature of the content of the footage, it would be inappropriate to make any further comment on the footage while other investigations are undertaken."
"This was not a passenger booking, the driver had logged off and was not working for fonacab at the time of the incident," a spokesperson said.
"We will however state that any action which affects the safety of our passengers, staff and drivers is never acceptable and should any infringement occur will be dealt with immediately by fonacab and referred to the appropriate authorities.
"Drivers at fonacab complete the same training and vetting as all taxi drivers in Northern Ireland and in addition we expect them to maintain the high standards that we hold ourselves to.
"We average 100,000 bookings per week, and we do everything we can to ensure that each of those customers is given the same high level of professional service. We do not tolerate incidents like this where safety is compromised, standards are not upheld, or the company and our drivers are called into disrepute."
A PSNI spokesperson said police "are aware of a video circulating online showing a man with a suspected firearm and have launched an investigation".
They added: "We would appeal to anyone with any information to contact Police on 101 or a report can be submitted online at www.psni.police.uk/makeareport/.
A spokesperson for the Department for Infrastructure's Driver & Vehicle Agency said: “The DVA has been made aware of the video circulating on social media. The department understands this matter is now under investigation by the PSNI and it would not be appropriate to provide any further comment at this time.”