A 36-year-old man has been charged with terrorism offences in connection with the murder of prison officer David Black.
He is due to appear at a Lisburn court on Thursday.
Mr Black, a 52-year-old father of two, was shot as he drove to work on the M1 near Portadown and Lurgan on November 1.
He had been driving to his work at Maghaberry Prison. A man, 44, and woman, 31, were arrested in Dublin on Tuesday.
Mr Black was the first prison officer to be murdered in Northern Ireland in 20 years.
A new dissident republican paramilitary group calling itself the IRA has claimed the responsibility for the killing