It is part of an ongoing investigation into the activities of the New IRA.
PSNI crime operations assistant chief constable Barbara Gray said: “Detectives from the Police Service of Northern Ireland’s Terrorism Investigation Unit have today searched properties at four locations in Belfast, Dungannon, Newry and Derry/Londonderry in connection with an ongoing investigation into the activities of the New IRA.
“The properties were searched under TACT (terrorism) legislation as part of Operation Arbacia, a community safety operation.”
The New IRA is a large dissident republican group which has targeted police officers.
A gunman from the armed group shot journalist Lyra McKee dead while she observed a riot in Derry in April last year.
Nine people were arrested on Tuesday as part of an MI5 and PSNI operation against the New IRA.
