A 50-year-old man has been arrested this afternoon by detectives investigating the explosion outside Bishop Street Courthouse in Derry on Saturday.
The man has been arrested under the Terrorism Act, and is the fifth person to be held in relation to the incident.
Four other men aged from 21 to 42, who were arrested in connection with the explosion, remain in police custody.
No-one was injured in the blast.
The 50-year-old man has also been arrested under the Terrorism Act in connection with an armed robbery in the Meadowbank Avenue area of the city on Tuesday, January 15.