A 23-year-old man has been charged with last December's £26½ million robbery at the Northern Bank.
The man is due before magistrates at Belfast's Laganside court this morning.
He faces charges of falsely imprisoning bank official Kevin McMullan and his wife Karen in Co Down, possession of a firearm or imitation firearm with intent to commit an indictable offence, and the robbery of £26½ million (nearly €40 million) from the Northern Bank in Belfast.
In addition to the charged man, four people, including a leading republican figure, were last night being detained for questioning in relation to the robbery.
The PSNI made two arrests early yesterday in Co Tyrone in addition to the two arrests made in south Down and one in Belfast on Wednesday.
Last night a 25 year old was released.
Sinn Féin denounced the arrests as a "stunt", while Sir Hugh Orde, the Chief Constable, said the arrests were a deeply significant part of investigation into the robbery.
"This is not over yet," the Chief Constable said.
"Just because people have been arrested today does not mean the investigation is closing down. The action we have taken is proportionate and has been the right thing to do. I have absolute confidence my detectives are looking in the right direction."
The wife of the arrested republican accused police of acting to denigrate the republican movement. "This is all a political exercise," she said. "This is to humiliate republicans again."
The Sinn Fein Fermanagh-South Tyrone MP Michelle Gildernew said: "The PSNI operation against republicans is without doubt driven by the political agenda of the RUC old guard in the Special Branch.
"Yesterday's Special Branch briefing of the usual selected sources in the media, and the unprecedented naming of those arrested by certain media outlets points all of us in that direction.
"I have no doubt that these briefings will continue today and attempts will be made to smear those arrested through the media. The operation in Tyrone overnight has been heavy-handed, unwarranted and completely without justification.
"These are not the actions of an accountable and acceptable policing service," she went on. "The operation in Tyrone will further undermine the confidence of the nationalist community in the ability of the PSNI to impartial, accountable policing and of course raises very serious questions for the SDLP."
Taoiseach Bertie Ahern was asked about the arrests on his visit to Belfast yesterday.
Asked could the Northern Bank arrests have any implications for the political process, Mr Ahern replied: "No, that's an ongoing policing matter."