Three members of the Irish Republican Socialist Party, the INLA's political wing, are being questioned in Gough barracks in Armagh about the murder of the paramilitary group's former chief of staff.
Mr Hugh Torney was shot dead in Lurgan, Co Armagh in September after a nine month feud in the organisation. It had its origins in Mr Torney's decision to call an INLA ceasefire last year.
The paramilitary group's leadership said he lacked the authority to do so. Mr Torney's murder marked the defeat of his faction. Two of the men being questioned are from Belfast. The other is from Lurgan.