It is believed a massive drugs and guns smuggling operation, which Gardaí intercepted yesterday, was masterminded from a prison cell.
More than 40 weapons were seized in Dublin and Belfast along with €4m worth of heroin and cannabis.
A 42-year-old Tipperary man was arrested in Dublin, and a man in his 30s was arrested at a Belfast Hotel.
It is thought both men were associates of Brian Meehan, who is behind bars for his part in the murder of journalist Veronica Guerin.