Three men and a teenager have been arrested in Londonderry in connection with dissident republican activity.
The men, aged 54, 42, 23 and a 16-year-old boy were arrested on Tuesday evening and taken to Antrim police station for questioning.
The 23-year-old was arrested in a car in Abercorn Road, where a suspected rifle was recovered by police.
The other three suspects, who were not in the car, were detained a short time later as part of a follow-up operation.
As part of the subsequent follow up an object was discovered, it was removed for examination by ATO. Searches are continuing in the area this afternoon.
A police spokesman said detectives from the serious crime squad made the arrests under the Terrorism Act.
Police said that the suspected firearm had been taken away for examination.
A suspicious object was also discovered by officers during the operation on the Foyle Road. The road has now re-opened.
A number of residents were temporarily evacuated from the homes and accommodated at Brooke Park Leisure Centre.
SDLP councillor John Boyle visited the scene on Tuesday night.
He said: "From speaking to local people I can confirm that witnesses saw a police vehicle ram another vehicle on the Foyle Road close to Craigavon Bridge, which is quite close to the city centre.
"The occupants of that vehicle were subsequently apprehended."