A man is being questioned by police in Belfast as part of an ongoing investigation into dissident republican terrorist activity.
Detectives from Serious Crime Branch arrested the 36-year-old in the Newry area on Sunday morning and took him to Musgrave Police Station serious crime suite for questioning.
A PSNI spokesman said a property was also searched as part of the investigation.
A 35-year-old man arrested in west Belfast on Saturday has been released unconditionally.
Three other men, aged 39, 40 and 47 remain in police custody.
Meanwhile, a security alert on the railway line in Lurgan has been lifted.
Trains were stopped following a report that that a device had been left on the line. Police said nothing was found following a check of the line.
