Sean Hoey is to face a total of 61 new charges, including the Omagh bomb murders, when he appears in court next week.
Hoey, who is 35 and from south Armagh, is currently being held on a number of other charges, including membership of the Real IRA.
The announcement of the additional charges was made at a remand hearing in Craigavon this morning.
His solicitor, Peter Corrigan, said he would launch an abuse of process application in an attempt to have the proceedings stopped.
Mr Corrigan said that throughout earlier discussions about the case there was no mention of impending murder charges.
