Officers came under sustained attack for a number of hours with more than 100 petrol bombs thrown at police cordons in the area of the Lake Street alert.
A PSNI spokesperson said: “Twenty five paint bombs, bricks and other masonry were also thrown by a large and aggressive crowd who gathered at around 9pm and remained until the early hours of the morning.
“Fortunately no police officers or members of the public were injured however a number of police vehicles were damaged.
Superintendent David Moore has hit out at those responsible: “The behaviour of those involved in the disorder last night was nothing short of disgusting. At one point a gunman emerged from this crowd and fired at least one shot at police. Mercifully no one was hurt.
“Local police officers and TSG colleagues were on the receiving end of orchestrated, intense and prolonged violence for a number of hours last night, all while trying to keep this community safe from what is potentially an explosive device close the railway line.
“We are extremely fortunate this morning not to be talking about officers being seriously injured simply while trying to do their job.
“I am grateful to the officers who were on duty last night for their professionalism and resilience and for the contribution they make to keeping this community safe in extremely challenging circumstances.
“A methodical clearance operation to dispose of the device will continue today and this is likely to cause disruption not only to rail travel in the area but also to the daily lives of people living close by. It will be necessary to evacuate a number of homes and we have already been in touch with most of the householders who will be affected by this operation.
“I am grateful for the cooperation and support of the broader community in Lurgan and I would ask that those who engaged in last night’s despicable disorder, seriously consider the consequences of their actions and the impact they are having not only on their community police officers but also on their community itself.”
The security operatin is ongoing causing major disruption to rail commuters.
The alert started on Sunday morning. However it was called off.
Though later a cameraman from UTV discovered a device laying on the side of the track near a residential area on Sunday.
A bus service has been put in place by Translink while the alert continues.
That will operate between Belfast Central and Newry Rail Stations (both ways) and trains will still run between Portadown to Newry and Dublin (both ways).