Three men arrested yesterday remain in custody
Detectives from the PSNI's Paramilitary Crime Task Force arrested a 27-year-old man in Derry on Wednesday.
The arrest is part of an ongoing investigation into INLA activity in the area.
The man was taken to Musgrave Serious Crime Suite for questioning.
Three men aged 30, 36 & 44 arrested on, Tuesday remain in police custody.
The Paramilitary Crime Task Force is made up of PSNI officers, HM Revenue & Customs officers and National Crime Agency officers and was formed to tackle paramilitary activity and organised crime in Northern Ireland.